Phase 3 scaffold: chat engine (WebSocket, FCM, pricing, timer, extension, history)

- Backend: WebSocket plugin, chat/pricing/timer/extension/closure/notification services
- Client app: ChatBloc, pricing dialog, chat screen with message status, extension/goodbye flow, history
- Mitra app: MitraChatBloc, ExtensionBloc, chat screen, extension accept/reject, history
- Control center: free trial, extension timeout, early end config toggles
- DB migration: chat_messages, session_closures, session_extensions, customer_transactions tables

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

client_app/lib/main.dart

@@ -1,9 +1,12 @@
 import 'package:firebase_core/firebase_core.dart';
+import 'package:firebase_messaging/firebase_messaging.dart';
 import 'package:flutter/material.dart';
 import 'package:flutter_bloc/flutter_bloc.dart';
 import 'package:go_router/go_router.dart';
 import 'core/api/api_client.dart';
 import 'core/auth/auth_bloc.dart';
+import 'core/chat/chat_bloc.dart';
+import 'core/chat/session_closure_bloc.dart';
 import 'core/pairing/pairing_bloc.dart';
 import 'firebase_options.dart';
 import 'router.dart';
@@ -11,6 +14,11 @@ import 'router.dart';
 void main() async {
   WidgetsFlutterBinding.ensureInitialized();
   await Firebase.initializeApp(options: DefaultFirebaseOptions.currentPlatform);
+
+  // Request notification permission
+  final messaging = FirebaseMessaging.instance;
+  await messaging.requestPermission();
+
   runApp(const App());
 }
 
@@ -31,6 +39,21 @@ class _AppState extends State<App> {
     super.initState();
     _authBloc = AuthBloc(apiClient: _apiClient)..add(AppStarted());
     _router = buildRouter(_authBloc);
+    _registerFcmToken();
+  }
+
+  Future<void> _registerFcmToken() async {
+    // Listen for auth state, then register token
+    _authBloc.stream.listen((state) async {
+      if (state is AuthAuthenticated || state is AuthAnonymous) {
+        try {
+          final token = await FirebaseMessaging.instance.getToken();
+          if (token != null) {
+            await _apiClient.post('/api/shared/device-token', data: {'token': token});
+          }
+        } catch (_) {}
+      }
+    });
   }
 
   @override
@@ -46,6 +69,8 @@ class _AppState extends State<App> {
       providers: [
         BlocProvider.value(value: _authBloc),
         BlocProvider(create: (_) => PairingBloc(apiClient: _apiClient)),
+        BlocProvider(create: (_) => ChatBloc(apiClient: _apiClient)),
+        BlocProvider(create: (_) => SessionClosureBloc(apiClient: _apiClient)),
         RepositoryProvider.value(value: _apiClient),
       ],
       child: MaterialApp.router(