Live wall: selected incident loads its own calls; resolved deep links; scrubber marks unloaded time (#239)

- LiveView: the selected incident merges useCallsByIncident (org_id +
  incident_ids CONTAINS, existing index, no orderBy/limit) into the calls fed
  to IncidentPanel and MapView, so a long incident keeps its full path and
  spine past the 500-call window. Stale rows from the previous selection are
  re-checked against the current id before merging.
- #inc= not in the active set is fetched with useIncident: a resolved one is
  selected, drawn on the map and shown under a "Resolved HH:MM" banner; a
  missing or other-org id shows "Incident not found". Auto-tour stays on
  active incidents.
- TimeScrubber: new loadedSince prop (oldest call when the window came back
  full). The axis before it is hatched and labelled "not loaded" instead of
  reading as a quiet stretch.
- useCalls returns hasMore (full page, counted before the duplicate_of
  filter); useIncident resets loading on a new id so a lookup doesn't flash
  "not found".

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

drb-frontend/lib/useIncidents.ts

@@ -89,6 +89,9 @@ export function useIncident(incidentId: string | null) {
 
   useEffect(() => {
     if (!incidentId) { setLoading(false); return; }
+    // A new id is a new lookup: without this, `loading` stays false from the
+    // previous id and a caller reads "not found" until the snapshot lands.
+    setLoading(true);
     let unsubFirestore: (() => void) | undefined;
 
     const unsubAuth = onAuthStateChanged(auth, (user) => {