Phase 2 refinements: Firebase config, dev environment fixes, phase 3 requirement draft

- Integrated Firebase SDK in both Flutter apps (google-services, firebase_options)
- Fixed auth flow, API client, and pairing/status blocs for dev environment
- Added full Flutter project scaffolds (android, ios, web, etc.)
- Added phase 3 chat engine requirement document
- Added bugreport zip pattern to gitignore

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

mitra_app/lib/core/status/status_bloc.dart

@@ -95,17 +95,16 @@ class StatusBloc extends Bloc<StatusEvent, StatusState> {
   }
 
   Future<void> _onAppPaused(AppPaused event, Emitter<StatusState> emit) async {
-    if (state is StatusLoaded && (state as StatusLoaded).isOnline) {
-      try {
-        await apiClient.post('/api/mitra/status/offline');
-      } catch (_) {}
-      _stopHeartbeat();
-      emit(StatusLoaded(isOnline: false));
-    }
+    // Don't auto-offline on pause — heartbeat timeout (45s) handles truly offline mitras.
+    // This allows mitra to stay online when briefly switching apps.
+    _stopHeartbeat();
   }
 
   Future<void> _onAppResumed(AppResumed event, Emitter<StatusState> emit) async {
-    // Do NOT auto-set online on resume; mitra must explicitly toggle
+    // Resume heartbeat if mitra was online
+    if (state is StatusLoaded && (state as StatusLoaded).isOnline) {
+      _startHeartbeat();
+    }
     add(StatusLoadRequested());
   }