feat: monitoring session improvements — UTC fix, period hours, calendar, session detail

- Fix UTC display bug: upload_nrl_data now wraps RNH datetimes with
  local_to_utc() before storing, matching patch_session behavior.
  Period type and label are derived from local time before conversion.

- Add period_start_hour / period_end_hour to MonitoringSession model
  (nullable integers 0–23). Migration: migrate_add_session_period_hours.py

- Update patch_session to accept and store period_start_hour / period_end_hour.
  Response now includes both fields.

- Update get_project_sessions to compute "Effective: M/D H:MM AM → M/D H:MM AM"
  string from period hours and pass it to session_list.html.

- Rework period edit UI in session_list.html: clicking the period badge now
  opens an inline editor with period type selector + start/end hour inputs.
  Selecting a period type pre-fills default hours (Day: 7–19, Night: 19–7).

- Wire period hours into _build_location_data_from_sessions: uses
  period_start/end_hour when set, falls back to hardcoded defaults.

- RND viewer: inject SESSION_PERIOD_START/END_HOUR from template context.
  renderTable() dims rows outside the period window (opacity-40) with a
  tooltip; shows "(N in period window)" in the row count.

- New session detail page at /api/projects/{id}/sessions/{id}/detail:
  shows breadcrumb, files list with View/Download/Report actions,
  editable session info form (label, period type, hours, times).

- Add local_datetime_input Jinja filter for datetime-local input values.

- Monthly calendar view: new get_sessions_calendar endpoint returns
  sessions_calendar.html partial; added below sessions list in detail.html.
  Color-coded per NRL with legend, HTMX prev/next navigation, session dots
  link to detail page.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

templates/partials/projects/sessions_calendar.html

@@ -0,0 +1,91 @@
+<!-- Monthly Sessions Calendar -->
+<div class="bg-white dark:bg-slate-800 rounded-xl border border-gray-200 dark:border-gray-700 overflow-hidden">
+
+    <!-- Calendar header: month navigation -->
+    <div class="px-5 py-3 border-b border-gray-200 dark:border-gray-700 flex items-center justify-between">
+        <button hx-get="/api/projects/{{ project_id }}/sessions-calendar?month={{ prev_month }}&year={{ prev_year }}"
+                hx-target="#sessions-calendar"
+                hx-swap="innerHTML"
+                class="p-1.5 rounded-lg hover:bg-gray-100 dark:hover:bg-slate-700 transition-colors text-gray-500 dark:text-gray-400"
+                title="Previous month">
+            <svg class="w-4 h-4" 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"></path>
+            </svg>
+        </button>
+
+        <h3 class="text-sm font-semibold text-gray-800 dark:text-gray-200">{{ month_name }} {{ year }}</h3>
+
+        <button hx-get="/api/projects/{{ project_id }}/sessions-calendar?month={{ next_month }}&year={{ next_year }}"
+                hx-target="#sessions-calendar"
+                hx-swap="innerHTML"
+                class="p-1.5 rounded-lg hover:bg-gray-100 dark:hover:bg-slate-700 transition-colors text-gray-500 dark:text-gray-400"
+                title="Next month">
+            <svg class="w-4 h-4" 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"></path>
+            </svg>
+        </button>
+    </div>
+
+    <!-- Legend -->
+    {% if legend %}
+    <div class="px-5 py-2 border-b border-gray-100 dark:border-gray-700 flex flex-wrap gap-3">
+        {% for loc in legend %}
+        <div class="flex items-center gap-1.5 text-xs text-gray-600 dark:text-gray-400">
+            <span class="w-2.5 h-2.5 rounded-full shrink-0" style="background-color: {{ loc.color }}"></span>
+            <span>{{ loc.name }}</span>
+        </div>
+        {% endfor %}
+    </div>
+    {% endif %}
+
+    <!-- Day-of-week headers -->
+    <div class="grid grid-cols-7 border-b border-gray-100 dark:border-gray-700">
+        {% for day_name in ['Mon', 'Tue', 'Wed', 'Thu', 'Fri', 'Sat', 'Sun'] %}
+        <div class="py-2 text-center text-xs font-medium text-gray-400 dark:text-gray-500 uppercase tracking-wide
+                    {% if loop.index >= 6 %}text-amber-500 dark:text-amber-400{% endif %}">
+            {{ day_name }}
+        </div>
+        {% endfor %}
+    </div>
+
+    <!-- Calendar grid -->
+    {% for week in weeks %}
+    <div class="grid grid-cols-7 {% if not loop.last %}border-b border-gray-100 dark:border-gray-700{% endif %}">
+        {% for day in week %}
+        <div class="min-h-[72px] p-1.5 {% if not loop.last %}border-r border-gray-100 dark:border-gray-700{% endif %}
+                    {% if not day.in_month %}bg-gray-50 dark:bg-slate-800/50{% else %}bg-white dark:bg-slate-800{% endif %}
+                    {% if day.is_today %}ring-1 ring-inset ring-seismo-orange{% endif %}">
+
+            <!-- Date number -->
+            <div class="text-right mb-1">
+                <span class="text-xs {% if day.is_today %}font-bold text-seismo-orange{% elif day.in_month %}text-gray-700 dark:text-gray-300{% else %}text-gray-300 dark:text-gray-600{% endif %}">
+                    {{ day.date.day }}
+                </span>
+            </div>
+
+            <!-- Session dots/chips -->
+            {% if day.sessions %}
+            <div class="space-y-0.5">
+                {% for s in day.sessions[:4] %}
+                <a href="/api/projects/{{ project_id }}/sessions/{{ s.session_id }}/detail"
+                   class="flex items-center gap-1 px-1 py-0.5 rounded text-xs truncate hover:opacity-80 transition-opacity"
+                   style="background-color: {{ s.color }}22; border-left: 2px solid {{ s.color }};"
+                   title="{{ s.label }}">
+                    <span class="truncate text-gray-700 dark:text-gray-300" style="color: {{ s.color }}; font-size: 0.65rem; line-height: 1.2;">
+                        {{ s.location_name }}
+                        {% if s.period_type %}
+                        <span class="opacity-60">{{ '☀' if 'day' in s.period_type else '☾' }}</span>
+                        {% endif %}
+                    </span>
+                </a>
+                {% endfor %}
+                {% if day.sessions|length > 4 %}
+                <div class="text-center text-xs text-gray-400 dark:text-gray-500">+{{ day.sessions|length - 4 }} more</div>
+                {% endif %}
+            </div>
+            {% endif %}
+        </div>
+        {% endfor %}
+    </div>
+    {% endfor %}
+</div>