fix(frontend): issues from the 10-25 Chrome sweep

- Incident detail "← Incidents" used router.back(), so arriving from Live
  or a shared link it went to the map / out of the app. Now a Link.
- Resolved incidents showed "0m elapsed" (manual resolve sets no
  resolved_at, updated_at can predate the last call): end is now the
  latest of resolved_at, updated_at and the newest call.
- Admin: the max-width toggle wrapped the tab bar, so it reflowed on every
  tab switch and left the cursor over e.g. "Close calls". Body only now.
- STT Eval sat on "Loading…" forever when a scanned page had zero matches
  but a next_cursor — the refill effect didn't depend on cursor.
- Trip event blocks used dark-only bg-indigo-950/60: unreadable in light
  mode. Theme tokens now.
- Reassign modal said "connected for the first time" on configured nodes.
- Dark-mode placeholders dimmed + italic; they read as filled-in values.

Frontend unverified locally (no Node, #207); CI build typechecks.

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

drb-frontend/lib/types.ts

@@ -487,6 +487,8 @@ export interface IncidentRecord {
   title: string | null;
   type: string | null;
   status: "active" | "resolved";
+  /** Set by the idle sweep; a manual resolve (PUT /incidents) doesn't set it. */
+  resolved_at?: string | null;
   location: string | null;
   location_coords: GeoPoint | null;
   /**