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>

client_app/lib/router.dart

@@ -1,3 +1,4 @@
+import 'dart:async';
 import 'package:flutter/material.dart';
 import 'package:go_router/go_router.dart';
 import 'core/auth/auth_bloc.dart';
@@ -12,14 +13,33 @@ import 'features/chat/screens/bestie_found_screen.dart';
 import 'features/chat/screens/no_bestie_screen.dart';
 import 'features/chat/screens/session_active_screen.dart';
 
+/// Converts a BLoC stream into a ChangeNotifier for GoRouter's refreshListenable.
+class _BlocRefreshNotifier extends ChangeNotifier {
+  late final StreamSubscription _subscription;
+
+  _BlocRefreshNotifier(AuthBloc bloc) {
+    _subscription = bloc.stream.listen((_) => notifyListeners());
+  }
+
+  @override
+  void dispose() {
+    _subscription.cancel();
+    super.dispose();
+  }
+}
+
 GoRouter buildRouter(AuthBloc authBloc) {
   return GoRouter(
     initialLocation: '/welcome',
+    refreshListenable: _BlocRefreshNotifier(authBloc),
     redirect: (context, state) {
       final authState = authBloc.state;
       final isAuthRoute = state.matchedLocation.startsWith('/auth') ||
           state.matchedLocation == '/welcome';
 
+      // Don't redirect while loading — stay on current screen
+      if (authState is AuthLoading) return null;
+
       if (authState is AuthAuthenticated || authState is AuthAnonymous) {
         return isAuthRoute ? '/home' : null;
       }