feat(tools): fleet-wide deployment history calendar (Phase 2)

The per-unit Gantt chart on /unit/{id} (Phase 1, v0.11.0) was scoped
to one unit's deployment timeline.  This adds the fleet-wide view as
a new entry under /tools.

What it shows
- 12-month calendar grid styled like the Job Planner (4 months per
  row, responsive down to single column on mobile).
- Each day cell shows up to 4 colored mini-bars — one per project
  that had ≥1 active UnitAssignment that day, color deterministically
  hashed from project_id.  Days with >4 active projects show "+N".
- KPI strip at the top: project count, distinct unit count, total
  assignment count in the window.
- Collapsible project legend: ordered by first-active date (which
  matches the deployment-history reading order), each row links to
  the project page, shows the assignment count.

Click-a-day side panel
- Click any populated day cell → slide-over panel from the right
- Groups by project, lists every (unit, location) active that day
- Per-deployment: unit link, location link, window dates, active /
  closed badge, "auto-backfilled" tag for metadata_backfill source
- Sources from a new GET /api/admin/deployment-history/day endpoint

Navigation
- Prev / Next month buttons shift the 12-month window by one month
- "Recent" button jumps back to default (12 months ending now)
- Default window is 11 months back from current month — operator
  sees the recent past on first load, not future emptiness

Files
- backend/services/deployment_history.py — data builder + day-detail
  helper.  Walks UnitAssignment windows, intersects with the 12-month
  range, computes per-project active-day sets.
- backend/routers/deployment_history.py — page route + day-detail JSON
  endpoint.  Wired into main.py.
- templates/admin/deployment_history.html — page + side-panel
- templates/tools.html — new card linking to the page

Phase 3 (deferred): drag-to-resize bars to retroactively adjust
assignment windows from inside the calendar; per-unit row view
(complement to the project-row view) for "where has unit X been across
all jobs"; horizontal scroll for >12-month windows.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

backend/main.py

@@ -109,6 +109,9 @@ app.include_router(watcher_manager.router)
 from backend.routers import admin_modules
 app.include_router(admin_modules.router)
 
+from backend.routers import deployment_history
+app.include_router(deployment_history.router)
+
 # Projects system routers
 app.include_router(projects.router)
 app.include_router(project_locations.router)

backend/routers/deployment_history.py

@@ -0,0 +1,99 @@
+"""
+Fleet-wide deployment-history calendar — Phase 2 of the
+deployment-history visualisation work (Phase 1 is the per-unit Gantt
+on /unit/{id}).
+
+Renders all UnitAssignment windows across all projects on a 12-month
+calendar grid styled like the Job Planner.  Each day cell shows one
+mini-bar per project that had ≥1 active assignment that day.  Click a
+day → side panel with the (unit, location) pairs active.
+
+Routes:
+  GET  /tools/deployment-history              — HTML page
+  GET  /api/admin/deployment-history/day      — JSON list of deployments
+                                                 on a specific date (used
+                                                 by the day-detail panel)
+"""
+
+from __future__ import annotations
+
+from datetime import date, datetime
+from typing import Optional
+
+from fastapi import APIRouter, Depends, Query, Request
+from fastapi.responses import HTMLResponse, JSONResponse
+from sqlalchemy.orm import Session
+
+from backend.database import get_db
+from backend.services.deployment_history import (
+    get_deployment_history_data,
+    get_deployments_on_day,
+)
+from backend.templates_config import templates
+
+router = APIRouter()
+
+
+@router.get("/tools/deployment-history", response_class=HTMLResponse)
+def deployment_history_page(
+    request: Request,
+    year:  Optional[int] = Query(None),
+    month: Optional[int] = Query(None),
+    db: Session = Depends(get_db),
+):
+    """Fleet-wide deployment history calendar.
+
+    Defaults to a 12-month window ending in the current month (so the
+    operator sees the recent past, not the future).  ?year=&month= can
+    override the START of the window to scroll backward or forward.
+    """
+    today = date.today()
+    # Default: 12-month window ending this month → start = 11 months back.
+    if year is None or month is None:
+        # 11 months back from current month.
+        m = today.month - 11
+        y = today.year
+        while m < 1:
+            m += 12
+            y -= 1
+        start_year, start_month = y, m
+    else:
+        start_year, start_month = year, month
+
+    calendar = get_deployment_history_data(db, start_year, start_month)
+
+    # Build prev/next navigation values.
+    prev_y, prev_m = (start_year - 1, 12) if start_month == 1 else (start_year, start_month - 1)
+    next_y, next_m = (start_year + 1, 1) if start_month == 12 else (start_year, start_month + 1)
+
+    return templates.TemplateResponse("admin/deployment_history.html", {
+        "request":  request,
+        "calendar": calendar,
+        "today":    today.isoformat(),
+        "prev_year":  prev_y,
+        "prev_month": prev_m,
+        "next_year":  next_y,
+        "next_month": next_m,
+    })
+
+
+@router.get("/api/admin/deployment-history/day")
+def deployment_history_day(
+    target_date: str = Query(..., description="YYYY-MM-DD"),
+    db: Session = Depends(get_db),
+):
+    """Return assignments active on a specific calendar day."""
+    try:
+        d = date.fromisoformat(target_date)
+    except ValueError:
+        return JSONResponse(
+            {"error": f"Invalid date: {target_date!r}"},
+            status_code=400,
+        )
+
+    deployments = get_deployments_on_day(db, d)
+    return JSONResponse({
+        "date":        target_date,
+        "count":       len(deployments),
+        "deployments": deployments,
+    })

backend/services/deployment_history.py

@@ -0,0 +1,316 @@
+"""
+Deployment-history calendar service — builds the data structure for the
+fleet-wide deployment-history grid (`/tools/deployment-history`).
+
+For each calendar day in a 12-month window, computes which projects had
+at least one unit assigned to a location on that day.  Renders as
+multi-month grid (job-planner style) with project-colored bars per day.
+
+Distinct from `services/fleet_calendar_service.py` which renders
+forward-looking RESERVATIONS for the planner.  This one is purely
+historical / current — it walks `unit_assignments` instead of
+`job_reservations`.
+"""
+
+from __future__ import annotations
+
+import hashlib
+from datetime import date, datetime, timedelta
+from calendar import monthrange
+from typing import Optional
+
+from sqlalchemy.orm import Session
+from sqlalchemy import and_, or_
+
+from backend.models import Project, UnitAssignment
+
+
+# Color palette for projects without an explicit color attribute.  Chosen
+# to have decent contrast on both light and dark backgrounds; cycles
+# deterministically by SHA1(project_id).
+_PROJECT_COLOR_PALETTE = [
+    "#f48b1c", "#142a66", "#7d234d", "#0e7490", "#15803d",
+    "#a16207", "#9333ea", "#dc2626", "#0d9488", "#1d4ed8",
+    "#be185d", "#65a30d", "#0891b2", "#7c3aed", "#b91c1c",
+]
+
+
+def _color_for_project(project_id: str) -> str:
+    """Deterministic color assignment from a fixed palette."""
+    h = hashlib.sha1(project_id.encode("utf-8")).digest()[0]
+    return _PROJECT_COLOR_PALETTE[h % len(_PROJECT_COLOR_PALETTE)]
+
+
+def _month_short(m: int) -> str:
+    return ["Jan", "Feb", "Mar", "Apr", "May", "Jun",
+            "Jul", "Aug", "Sep", "Oct", "Nov", "Dec"][m - 1]
+
+
+def _month_full(m: int) -> str:
+    return ["January", "February", "March", "April", "May", "June",
+            "July", "August", "September", "October", "November", "December"][m - 1]
+
+
+def get_deployment_history_data(
+    db: Session,
+    start_year: int,
+    start_month: int,
+) -> dict:
+    """
+    Build the calendar data structure for a 12-month window starting at
+    (start_year, start_month).
+
+    Returns:
+        {
+          "months": [
+            {
+              "year": int,
+              "month": int,            # 1-12
+              "name": "January",
+              "short_name": "Jan",
+              "year_short": "26",
+              "num_days": int,
+              "first_weekday": int,    # 0=Mon..6=Sun (datetime.weekday())
+              "active_days": {
+                  day_num: [project_id, project_id, ...]  # projects with
+                                                          # ≥1 active assignment
+                                                          # on that day
+              },
+            },
+            ...                                          # 12 entries
+          ],
+          "projects": [
+            {
+              "id": str,
+              "name": str,
+              "color": str,
+              "status": str,
+              "client_name": str | None,
+              "assignment_count": int,    # total assignments contributing to
+                                          # this 12-month window
+              "first_active":   "YYYY-MM-DD" | None,
+              "last_active":    "YYYY-MM-DD" | None,
+            },
+            ...                                          # only projects with
+                                                         # ≥1 assignment in the
+                                                         # window, sorted by
+                                                         # first_active ASC
+          ],
+          "total_assignments": int,
+          "total_active_units": int,    # distinct unit_ids across the window
+          "window": {
+              "start_year": int,
+              "start_month": int,
+              "end_year": int,
+              "end_month": int,
+              "first_date": "YYYY-MM-DD",
+              "last_date":  "YYYY-MM-DD",
+          },
+        }
+    """
+    # Compute window edges.
+    first_date = date(start_year, start_month, 1)
+    # 12 months → end on day-1 of (start + 12)
+    end_year  = start_year + ((start_month + 10) // 12)
+    end_month = ((start_month + 10) % 12) + 1
+    last_date = date(end_year, end_month, monthrange(end_year, end_month)[1])
+
+    now = datetime.utcnow()
+
+    # Fetch every assignment that overlaps the window.  An assignment
+    # overlaps if assigned_at <= last_date AND (assigned_until is NULL
+    # OR assigned_until >= first_date).
+    assignments = (
+        db.query(UnitAssignment)
+        .filter(UnitAssignment.assigned_at <= datetime.combine(last_date, datetime.max.time()))
+        .filter(
+            or_(
+                UnitAssignment.assigned_until == None,   # noqa: E711 — active
+                UnitAssignment.assigned_until >= datetime.combine(first_date, datetime.min.time()),
+            )
+        )
+        .all()
+    )
+
+    # Resolve referenced projects in one query.
+    proj_ids = {a.project_id for a in assignments}
+    proj_map = {
+        p.id: p for p in db.query(Project).filter(Project.id.in_(proj_ids)).all()
+    } if proj_ids else {}
+
+    # Compute "active days per project" by walking each assignment and
+    # adding every day in its [start, end] ∩ [first_date, last_date].
+    # O(N_assignments × avg_window_days); for a typical fleet this is
+    # bounded (hundreds of assignments × hundreds of days = manageable).
+    project_active_days: dict[str, set[date]] = {}
+    project_first_active: dict[str, date] = {}
+    project_last_active:  dict[str, date] = {}
+    project_assignment_count: dict[str, int] = {}
+    distinct_units: set[str] = set()
+
+    for a in assignments:
+        start = max(a.assigned_at.date() if a.assigned_at else first_date, first_date)
+        end_dt = a.assigned_until or now
+        end   = min(end_dt.date(), last_date)
+        if end < start:
+            continue
+        days = project_active_days.setdefault(a.project_id, set())
+        d = start
+        while d <= end:
+            days.add(d)
+            d += timedelta(days=1)
+        project_assignment_count[a.project_id] = project_assignment_count.get(a.project_id, 0) + 1
+        distinct_units.add(a.unit_id)
+        # Track first/last active dates in the window.
+        prev_first = project_first_active.get(a.project_id)
+        if prev_first is None or start < prev_first:
+            project_first_active[a.project_id] = start
+        prev_last = project_last_active.get(a.project_id)
+        if prev_last is None or end > prev_last:
+            project_last_active[a.project_id] = end
+
+    # Build the projects array (sorted by first_active ascending so the
+    # legend reads in deployment-order).
+    projects_data = []
+    for pid, days in project_active_days.items():
+        p = proj_map.get(pid)
+        if not p:
+            # Assignment references a deleted project — surface it anyway
+            # with a placeholder name, since the bars still need a label.
+            projects_data.append({
+                "id": pid,
+                "name": "(deleted project)",
+                "color": _color_for_project(pid),
+                "status": "deleted",
+                "client_name": None,
+                "assignment_count": project_assignment_count.get(pid, 0),
+                "first_active": project_first_active[pid].isoformat() if pid in project_first_active else None,
+                "last_active":  project_last_active[pid].isoformat()  if pid in project_last_active  else None,
+            })
+            continue
+        projects_data.append({
+            "id":     pid,
+            "name":   p.name,
+            "color":  _color_for_project(pid),
+            "status": p.status or "active",
+            "client_name":      p.client_name,
+            "assignment_count": project_assignment_count.get(pid, 0),
+            "first_active":     project_first_active[pid].isoformat() if pid in project_first_active else None,
+            "last_active":      project_last_active[pid].isoformat()  if pid in project_last_active  else None,
+        })
+
+    projects_data.sort(key=lambda p: (p["first_active"] or "9999", p["name"]))
+
+    # Now build the months array.
+    months_data = []
+    cur_year, cur_month = start_year, start_month
+    for _ in range(12):
+        num_days = monthrange(cur_year, cur_month)[1]
+        first_weekday = date(cur_year, cur_month, 1).weekday()   # 0=Mon..6=Sun
+        active_days: dict[int, list[str]] = {}
+        for day_num in range(1, num_days + 1):
+            d = date(cur_year, cur_month, day_num)
+            day_projects = [
+                pid for pid, days in project_active_days.items()
+                if d in days
+            ]
+            if day_projects:
+                # Sort by the project's color-stable order so bars don't
+                # jitter between days.
+                day_projects.sort()
+                active_days[day_num] = day_projects
+        months_data.append({
+            "year":         cur_year,
+            "month":        cur_month,
+            "name":         _month_full(cur_month),
+            "short_name":   _month_short(cur_month),
+            "year_short":   f"{cur_year % 100:02d}",
+            "num_days":     num_days,
+            "first_weekday": first_weekday,
+            "active_days":  active_days,
+        })
+        # Advance one month.
+        if cur_month == 12:
+            cur_year += 1
+            cur_month = 1
+        else:
+            cur_month += 1
+
+    return {
+        "months":   months_data,
+        "projects": projects_data,
+        "total_assignments":    len(assignments),
+        "total_active_units":   len(distinct_units),
+        "window": {
+            "start_year":  start_year,
+            "start_month": start_month,
+            "end_year":    end_year,
+            "end_month":   end_month,
+            "first_date":  first_date.isoformat(),
+            "last_date":   last_date.isoformat(),
+        },
+    }
+
+
+def get_deployments_on_day(
+    db: Session,
+    target_date: date,
+) -> list[dict]:
+    """
+    Return the list of (unit, location, project) tuples that were
+    actively assigned on a specific calendar date.  Used for the
+    day-detail side panel when an operator clicks a day cell.
+    """
+    from backend.models import MonitoringLocation, RosterUnit
+
+    day_start = datetime.combine(target_date, datetime.min.time())
+    day_end   = datetime.combine(target_date, datetime.max.time())
+
+    rows = (
+        db.query(UnitAssignment)
+        .filter(UnitAssignment.assigned_at <= day_end)
+        .filter(
+            or_(
+                UnitAssignment.assigned_until == None,   # noqa: E711
+                UnitAssignment.assigned_until >= day_start,
+            )
+        )
+        .order_by(UnitAssignment.project_id, UnitAssignment.unit_id)
+        .all()
+    )
+
+    if not rows:
+        return []
+
+    loc_ids = {a.location_id for a in rows}
+    proj_ids = {a.project_id for a in rows}
+    loc_map = {
+        l.id: l for l in db.query(MonitoringLocation).filter(
+            MonitoringLocation.id.in_(loc_ids)
+        ).all()
+    }
+    proj_map = {
+        p.id: p for p in db.query(Project).filter(
+            Project.id.in_(proj_ids)
+        ).all()
+    }
+
+    results = []
+    for a in rows:
+        loc  = loc_map.get(a.location_id)
+        proj = proj_map.get(a.project_id)
+        results.append({
+            "assignment_id":   a.id,
+            "unit_id":         a.unit_id,
+            "location_id":     a.location_id,
+            "location_name":   loc.name  if loc  else "(unknown location)",
+            "project_id":      a.project_id,
+            "project_name":    proj.name if proj else "(deleted project)",
+            "project_color":   _color_for_project(a.project_id),
+            "assigned_at":     a.assigned_at.isoformat()    if a.assigned_at    else None,
+            "assigned_until":  a.assigned_until.isoformat() if a.assigned_until else None,
+            "is_active":       a.assigned_until is None,
+            "source":          a.source,
+        })
+
+    return results

templates/admin/deployment_history.html

@@ -0,0 +1,346 @@
+{% extends "base.html" %}
+
+{% block title %}Deployment History - Seismo Fleet Manager{% endblock %}
+
+{% block extra_head %}
+<style>
+.dh-calendar-grid {
+    display: grid;
+    grid-template-columns: repeat(4, 1fr);
+    gap: 1rem;
+}
+@media (max-width: 1280px) { .dh-calendar-grid { grid-template-columns: repeat(3, 1fr); } }
+@media (max-width: 768px)  { .dh-calendar-grid { grid-template-columns: repeat(2, 1fr); } }
+@media (max-width: 480px)  { .dh-calendar-grid { grid-template-columns: 1fr; } }
+
+.dh-month-card {
+    background: white;
+    border-radius: 0.5rem;
+    padding: 0.75rem;
+    box-shadow: 0 1px 3px rgba(0,0,0,0.1);
+}
+.dark .dh-month-card { background: rgb(30 41 59); }
+
+.dh-day-grid {
+    display: grid;
+    grid-template-columns: repeat(7, 1fr);
+    gap: 2px;
+    font-size: 0.75rem;
+}
+.dh-day-header {
+    text-align: center;
+    font-weight: 600;
+    color: #6b7280;
+    padding: 0.25rem 0;
+}
+.dark .dh-day-header { color: #9ca3af; }
+
+.dh-day-cell {
+    aspect-ratio: 1;
+    display: flex;
+    flex-direction: column;
+    align-items: stretch;
+    justify-content: flex-start;
+    border-radius: 0.25rem;
+    position: relative;
+    transition: all 0.15s ease;
+    font-size: 0.7rem;
+    padding-top: 2px;
+    background-color: #f3f4f6;
+    color: #374151;
+    cursor: pointer;
+}
+.dh-day-cell:hover {
+    transform: scale(1.1);
+    z-index: 10;
+}
+.dh-day-cell.empty {
+    background: transparent;
+    cursor: default;
+}
+.dh-day-cell.empty:hover { transform: none; }
+.dh-day-cell.today {
+    ring-color: #f48b1c;
+    font-weight: 700;
+    color: #b84a12;
+}
+.dark .dh-day-cell {
+    background-color: rgba(55, 65, 81, 0.5);
+    color: #d1d5db;
+}
+.dh-day-cell .dh-day-num {
+    text-align: center;
+    flex-shrink: 0;
+}
+.dh-day-cell .dh-bars {
+    display: flex;
+    flex-direction: column;
+    gap: 1px;
+    margin: 2px 2px 0 2px;
+}
+.dh-bar {
+    height: 3px;
+    border-radius: 1px;
+}
+</style>
+{% endblock %}
+
+{% block content %}
+<div class="mb-6 flex items-center justify-between flex-wrap gap-3">
+    <div>
+        <a href="/tools" class="text-sm text-seismo-orange hover:text-seismo-burgundy">← Back to Tools</a>
+        <h1 class="text-3xl font-bold text-gray-900 dark:text-white mt-1">Deployment History</h1>
+        <p class="text-gray-600 dark:text-gray-400 mt-1">
+            Where every unit has been — actual assignment windows, color-coded by project.
+            For future / planned deployments use the <a href="/fleet-calendar" class="text-seismo-orange hover:text-seismo-burgundy">Job Planner</a>.
+        </p>
+    </div>
+</div>
+
+<!-- KPI strip -->
+<div class="flex flex-wrap items-center gap-4 mb-6">
+    <div class="flex items-center gap-3 text-sm bg-white dark:bg-slate-800 rounded-lg px-4 py-2 shadow">
+        <span class="text-gray-500 dark:text-gray-400">{{ calendar.projects | length }} project{{ '' if calendar.projects | length == 1 else 's' }}</span>
+        <span class="text-gray-300 dark:text-gray-600">|</span>
+        <span class="text-gray-500 dark:text-gray-400">{{ calendar.total_active_units }} unique units</span>
+        <span class="text-gray-300 dark:text-gray-600">|</span>
+        <span class="text-gray-500 dark:text-gray-400">{{ calendar.total_assignments }} assignment{{ '' if calendar.total_assignments == 1 else 's' }} in window</span>
+    </div>
+    {% if calendar.projects %}
+    <details class="bg-white dark:bg-slate-800 rounded-lg shadow px-4 py-2">
+        <summary class="cursor-pointer text-sm font-medium text-gray-700 dark:text-gray-300 select-none">Project legend</summary>
+        <div class="flex flex-wrap items-center gap-x-4 gap-y-2 mt-3 pt-3 border-t border-gray-200 dark:border-gray-700">
+            {% for p in calendar.projects %}
+            <a href="/projects/{{ p.id }}"
+               class="flex items-center gap-1.5 text-sm text-gray-700 dark:text-gray-300 hover:text-seismo-orange">
+                <span class="w-3 h-1.5 rounded-full flex-shrink-0" style="background-color: {{ p.color }};"></span>
+                {{ p.name }}
+                <span class="text-xs text-gray-400 dark:text-gray-500">·</span>
+                <span class="text-xs text-gray-500 dark:text-gray-400">{{ p.assignment_count }}</span>
+            </a>
+            {% endfor %}
+        </div>
+    </details>
+    {% endif %}
+</div>
+
+<!-- Calendar grid -->
+{% if calendar.projects %}
+<div class="dh-calendar-grid mb-6">
+    {% for month_data in calendar.months %}
+    <div class="dh-month-card">
+        <h3 class="font-semibold text-gray-900 dark:text-white mb-2 text-center">
+            {{ month_data.short_name }} '{{ month_data.year_short }}
+        </h3>
+        <div class="dh-day-grid">
+            <div class="dh-day-header">S</div>
+            <div class="dh-day-header">M</div>
+            <div class="dh-day-header">T</div>
+            <div class="dh-day-header">W</div>
+            <div class="dh-day-header">T</div>
+            <div class="dh-day-header">F</div>
+            <div class="dh-day-header">S</div>
+
+            {# Sunday-first alignment: shift Monday=0 → Sunday=0 #}
+            {% set first_offset = (month_data.first_weekday + 1) % 7 %}
+            {% for i in range(first_offset) %}
+                <div class="dh-day-cell empty"></div>
+            {% endfor %}
+
+            {% for day_num in range(1, month_data.num_days + 1) %}
+                {% set date_str = '%04d-%02d-%02d' | format(month_data.year, month_data.month, day_num) %}
+                {% set is_today = date_str == today %}
+                {% set day_proj_ids = month_data.active_days.get(day_num, []) %}
+                <div class="dh-day-cell{% if is_today %} today ring-2 ring-seismo-orange{% endif %}"
+                     onclick="openDhDay('{{ date_str }}')"
+                     title="{{ date_str }} — {{ day_proj_ids | length }} project{{ '' if day_proj_ids | length == 1 else 's' }}">
+                    <span class="dh-day-num">{{ day_num }}</span>
+                    {% if day_proj_ids %}
+                    <span class="dh-bars">
+                        {% for pid in day_proj_ids[:4] %}
+                            {% set p = (calendar.projects | selectattr('id', 'equalto', pid) | first) %}
+                            {% if p %}
+                            <span class="dh-bar" style="background-color: {{ p.color }};"
+                                  title="{{ p.name }}"></span>
+                            {% endif %}
+                        {% endfor %}
+                        {% if day_proj_ids | length > 4 %}
+                            <span class="text-[8px] text-gray-500 leading-none">+{{ day_proj_ids | length - 4 }}</span>
+                        {% endif %}
+                    </span>
+                    {% endif %}
+                </div>
+            {% endfor %}
+        </div>
+    </div>
+    {% endfor %}
+</div>
+
+<!-- Month navigation -->
+<div class="flex items-center justify-center gap-3 mb-8">
+    <a href="/tools/deployment-history?year={{ prev_year }}&month={{ prev_month }}"
+       class="px-3 py-2 rounded-lg bg-gray-100 dark:bg-gray-700 hover:bg-gray-200 dark:hover:bg-gray-600 text-gray-700 dark:text-gray-300"
+       title="Previous month">
+        <svg class="w-5 h-5" fill="none" stroke="currentColor" viewBox="0 0 24 24">
+            <path stroke-linecap="round" stroke-linejoin="round" stroke-width="2" d="M15 19l-7-7 7-7"/>
+        </svg>
+    </a>
+    <span class="text-lg font-bold text-gray-900 dark:text-white px-3">
+        {{ calendar.months[0].short_name }} '{{ calendar.months[0].year_short }} – {{ calendar.months[11].short_name }} '{{ calendar.months[11].year_short }}
+    </span>
+    <a href="/tools/deployment-history?year={{ next_year }}&month={{ next_month }}"
+       class="px-3 py-2 rounded-lg bg-gray-100 dark:bg-gray-700 hover:bg-gray-200 dark:hover:bg-gray-600 text-gray-700 dark:text-gray-300"
+       title="Next month">
+        <svg class="w-5 h-5" fill="none" stroke="currentColor" viewBox="0 0 24 24">
+            <path stroke-linecap="round" stroke-linejoin="round" stroke-width="2" d="M9 5l7 7-7 7"/>
+        </svg>
+    </a>
+    <a href="/tools/deployment-history"
+       class="ml-2 px-4 py-2 rounded-lg bg-seismo-orange text-white hover:bg-orange-600">
+        Recent
+    </a>
+</div>
+
+{% else %}
+<div class="bg-white dark:bg-slate-800 rounded-xl shadow-lg p-8 text-center text-gray-500 dark:text-gray-400">
+    <svg class="w-12 h-12 mx-auto mb-3 opacity-40" fill="none" stroke="currentColor" viewBox="0 0 24 24">
+        <path stroke-linecap="round" stroke-linejoin="round" stroke-width="2" d="M8 7V3m8 4V3m-9 8h10M5 21h14a2 2 0 002-2V7a2 2 0 00-2-2H5a2 2 0 00-2 2v12a2 2 0 002 2z"/>
+    </svg>
+    <p class="text-sm">No deployments in this window.</p>
+    <p class="text-xs mt-1">Try the navigation buttons below to look at a different range.</p>
+</div>
+{% endif %}
+
+<!-- Day-detail side panel -->
+<div id="dh-day-panel-backdrop"
+     class="fixed inset-0 bg-black/30 z-40 hidden transition-opacity"
+     onclick="closeDhDayPanel()"></div>
+<div id="dh-day-panel"
+     class="fixed top-0 right-0 h-screen w-full max-w-md bg-white dark:bg-slate-800 shadow-2xl z-50 hidden transform translate-x-full transition-transform duration-300 overflow-y-auto">
+    <div class="sticky top-0 bg-white dark:bg-slate-800 border-b border-gray-200 dark:border-gray-700 px-5 py-4 flex items-center justify-between">
+        <div>
+            <h2 class="text-lg font-semibold text-gray-900 dark:text-white" id="dh-day-panel-title">Deployments on…</h2>
+            <p class="text-xs text-gray-500 dark:text-gray-400" id="dh-day-panel-subtitle"></p>
+        </div>
+        <button onclick="closeDhDayPanel()" class="text-gray-400 hover:text-gray-700 dark:hover:text-gray-200">
+            <svg class="w-5 h-5" fill="none" stroke="currentColor" viewBox="0 0 24 24">
+                <path stroke-linecap="round" stroke-linejoin="round" stroke-width="2" d="M6 18L18 6M6 6l12 12"/>
+            </svg>
+        </button>
+    </div>
+    <div id="dh-day-panel-body" class="p-5 space-y-3">
+        <div class="text-center py-8 text-gray-500 dark:text-gray-400 text-sm">
+            <div class="animate-spin rounded-full h-6 w-6 border-b-2 border-seismo-orange mx-auto mb-2"></div>
+            Loading…
+        </div>
+    </div>
+</div>
+
+<script>
+function _dhEsc(s) {
+    if (s == null) return '';
+    return String(s).replace(/&/g, '&amp;').replace(/</g, '&lt;').replace(/>/g, '&gt;').replace(/"/g, '&quot;');
+}
+
+async function openDhDay(dateStr) {
+    const panel    = document.getElementById('dh-day-panel');
+    const backdrop = document.getElementById('dh-day-panel-backdrop');
+    const title    = document.getElementById('dh-day-panel-title');
+    const sub      = document.getElementById('dh-day-panel-subtitle');
+    const body     = document.getElementById('dh-day-panel-body');
+
+    title.textContent = 'Deployments on ' + dateStr;
+    sub.textContent   = '';
+    body.innerHTML    = `<div class="text-center py-8 text-gray-500 dark:text-gray-400 text-sm">
+        <div class="animate-spin rounded-full h-6 w-6 border-b-2 border-seismo-orange mx-auto mb-2"></div>
+        Loading…
+    </div>`;
+
+    panel.classList.remove('hidden');
+    backdrop.classList.remove('hidden');
+    requestAnimationFrame(() => panel.classList.remove('translate-x-full'));
+
+    try {
+        const r = await fetch(`/api/admin/deployment-history/day?target_date=${encodeURIComponent(dateStr)}`);
+        if (!r.ok) throw new Error('HTTP ' + r.status);
+        const d = await r.json();
+        renderDhDayPanel(d, dateStr);
+    } catch (e) {
+        body.innerHTML = `<p class="text-sm text-red-500">Failed to load: ${_dhEsc(e.message)}</p>`;
+    }
+}
+
+function renderDhDayPanel(d, dateStr) {
+    const sub  = document.getElementById('dh-day-panel-subtitle');
+    const body = document.getElementById('dh-day-panel-body');
+
+    sub.textContent = `${d.count} active deployment${d.count === 1 ? '' : 's'}`;
+
+    if (d.count === 0) {
+        body.innerHTML = '<p class="text-sm text-gray-500 dark:text-gray-400">No active deployments on this date.</p>';
+        return;
+    }
+
+    // Group by project for cleaner display.
+    const byProj = {};
+    for (const dep of d.deployments) {
+        const key = dep.project_id || '_none';
+        if (!byProj[key]) byProj[key] = { name: dep.project_name, color: dep.project_color, items: [] };
+        byProj[key].items.push(dep);
+    }
+
+    let html = '';
+    for (const pid of Object.keys(byProj)) {
+        const proj = byProj[pid];
+        html += `<div class="space-y-1">
+            <div class="flex items-center justify-between">
+                <a href="/projects/${_dhEsc(pid)}" class="flex items-center gap-2 font-medium text-gray-900 dark:text-white hover:text-seismo-orange">
+                    <span class="w-3 h-3 rounded-full" style="background-color: ${proj.color};"></span>
+                    ${_dhEsc(proj.name)}
+                </a>
+                <span class="text-xs text-gray-500 dark:text-gray-400">${proj.items.length} unit${proj.items.length === 1 ? '' : 's'}</span>
+            </div>
+            <div class="space-y-1 ml-5">`;
+        for (const dep of proj.items) {
+            const activeBadge = dep.is_active
+                ? '<span class="text-[10px] uppercase tracking-wider px-1 py-0.5 rounded bg-green-100 text-green-800 dark:bg-green-900/30 dark:text-green-300">active</span>'
+                : '';
+            const sourceTag = dep.source === 'metadata_backfill'
+                ? '<span class="text-[10px] text-blue-600 dark:text-blue-400 italic">auto-backfilled</span>'
+                : '';
+            const windowEnd = dep.is_active ? 'present' : (dep.assigned_until || '').slice(0, 10);
+            const windowStart = (dep.assigned_at || '').slice(0, 10);
+            html += `<div class="flex items-center justify-between gap-2 py-1 text-sm">
+                <div class="min-w-0 flex-1">
+                    <div class="flex items-center gap-2 flex-wrap">
+                        <a href="/unit/${_dhEsc(dep.unit_id)}" class="font-mono font-medium text-seismo-orange hover:text-seismo-navy">${_dhEsc(dep.unit_id)}</a>
+                        ${activeBadge}
+                        ${sourceTag}
+                    </div>
+                    <div class="text-xs text-gray-500 dark:text-gray-400 truncate">
+                        📍 <a href="/projects/${_dhEsc(pid)}/nrl/${_dhEsc(dep.location_id)}" class="hover:text-seismo-orange">${_dhEsc(dep.location_name)}</a>
+                    </div>
+                    <div class="text-[11px] text-gray-400 dark:text-gray-500 font-mono">${windowStart} → ${windowEnd}</div>
+                </div>
+            </div>`;
+        }
+        html += `</div></div>`;
+    }
+    body.innerHTML = html;
+}
+
+function closeDhDayPanel() {
+    const panel    = document.getElementById('dh-day-panel');
+    const backdrop = document.getElementById('dh-day-panel-backdrop');
+    panel.classList.add('translate-x-full');
+    setTimeout(() => {
+        panel.classList.add('hidden');
+        backdrop.classList.add('hidden');
+    }, 300);
+}
+
+document.addEventListener('keydown', (e) => {
+    if (e.key === 'Escape') closeDhDayPanel();
+});
+</script>
+{% endblock %}

templates/tools.html

@@ -68,6 +68,24 @@
         </div>
     </a>
 
+    <!-- Deployment History -->
+    <a href="/tools/deployment-history"
+       class="block bg-white dark:bg-slate-800 rounded-xl shadow-lg p-5 hover:shadow-xl transition-shadow border border-transparent hover:border-seismo-orange">
+        <div class="flex items-start gap-3">
+            <div class="w-10 h-10 rounded-lg bg-indigo-100 dark:bg-indigo-900/30 text-indigo-600 dark:text-indigo-400 flex items-center justify-center shrink-0">
+                <svg class="w-5 h-5" fill="none" stroke="currentColor" viewBox="0 0 24 24">
+                    <path stroke-linecap="round" stroke-linejoin="round" stroke-width="2" d="M8 7V3m8 4V3m-9 8h10M5 21h14a2 2 0 002-2V7a2 2 0 00-2-2H5a2 2 0 00-2 2v12a2 2 0 002 2z"/>
+                </svg>
+            </div>
+            <div class="flex-1 min-w-0">
+                <h3 class="font-semibold text-gray-900 dark:text-white">Deployment History</h3>
+                <p class="text-sm text-gray-600 dark:text-gray-400 mt-1">
+                    12-month calendar of every unit assignment across every project. Visual bars per project per day; click a day for the full active-deployments list.
+                </p>
+            </div>
+        </div>
+    </a>
+
     <!-- Reports (per-project) -->
     <a href="/projects"
        class="block bg-white dark:bg-slate-800 rounded-xl shadow-lg p-5 hover:shadow-xl transition-shadow border border-transparent hover:border-seismo-orange">