feat(sfm): project-level vibration events roll-up

Phase 3 of the SFM integration. Adds a "Project-wide vibration events"
KPI card to the Vibration tab of every project detail page, summarising
event activity across all of that project's vibration MonitoringLocations.

Backend:
- backend/services/sfm_events.py: vibration_summary_for_project() helper.
  Concurrently fans out events_for_location() across every vibration
  location in the project; aggregates total events, peak PVS (with the
  location it occurred at), last-event timestamp, false-trigger count;
  and produces a per-location breakdown sorted by event count.

- backend/routers/project_locations.py: new GET /api/projects/{p}/
  vibration_summary endpoint returning an HTML partial (HTMX-friendly,
  matches the locations-list HTMX pattern already used on this page).

Frontend:
- templates/partials/projects/vibration_summary.html: new partial with
  four KPI tiles (total, peak PVS + linked location + date, last event,
  false triggers) and a "Top locations by activity" mini-list showing
  the top 5 by event count.  Empty-state copy when the project has no
  vibration locations yet.

- templates/projects/detail.html: HTMX-load the new summary above the
  locations list inside the Vibration tab.

Verified against terra-view-alpha: 24 events across "Loc 1 - 78 poop
street", peak PVS 14.1351 in/s.

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

backend/routers/project_locations.py

@@ -776,6 +776,46 @@ async def get_nrl_sessions(
     })
 
 
+@router.get("/vibration_summary", response_class=HTMLResponse)
+async def get_project_vibration_summary(
+    project_id: str,
+    request: Request,
+    from_dt: Optional[datetime] = Query(None),
+    to_dt: Optional[datetime] = Query(None),
+    db: Session = Depends(get_db),
+):
+    """
+    Render a small HTML partial summarising vibration-event activity
+    across every vibration MonitoringLocation in the project.
+
+    Returned to the Vibration tab of the project detail page via HTMX.
+    Fans out concurrently across all locations (which in turn fan out
+    across each location's UnitAssignment windows).  Total queries to
+    SFM = sum of assignments across the project.
+
+    404 if the project doesn't exist.  Empty-state partial if the
+    project has no vibration locations.
+    """
+    project = db.query(Project).filter_by(id=project_id).first()
+    if not project:
+        raise HTTPException(status_code=404, detail="Project not found.")
+
+    from backend.services.sfm_events import vibration_summary_for_project
+
+    summary = await vibration_summary_for_project(
+        db, project_id, from_dt=from_dt, to_dt=to_dt
+    )
+
+    return templates.TemplateResponse(
+        "partials/projects/vibration_summary.html",
+        {
+            "request":    request,
+            "project_id": project_id,
+            "summary":    summary,
+        },
+    )
+
+
 @router.get("/locations/{location_id}/events", response_class=JSONResponse)
 async def get_location_events(
     project_id: str,