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>

templates/projects/detail.html

@@ -90,6 +90,17 @@
 
         <!-- Vibration Locations sub-panel -->
         <div id="vib-sub-locations" class="vib-sub-panel">
+            <!-- Project-wide vibration events roll-up -->
+            <div id="vibration-summary"
+                 hx-get="/api/projects/{{ project_id }}/vibration_summary"
+                 hx-trigger="load"
+                 hx-swap="innerHTML"
+                 class="mb-5">
+                <div class="bg-white dark:bg-slate-800 rounded-xl shadow-lg p-4">
+                    <div class="text-sm text-gray-500 dark:text-gray-400">Loading project summary…</div>
+                </div>
+            </div>
+
             <div class="bg-white dark:bg-slate-800 rounded-xl shadow-lg p-6">
                 <div class="flex items-center justify-between mb-6">
                     <h2 class="text-xl font-semibold text-gray-900 dark:text-white">Monitoring Locations</h2>