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>

mitra_app/lib/main.dart

@@ -1,4 +1,5 @@
 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';
@@ -6,12 +7,18 @@ import 'core/api/api_client.dart';
 import 'core/auth/auth_bloc.dart';
 import 'core/status/status_bloc.dart';
 import 'core/chat/chat_request_bloc.dart';
+import 'core/chat/mitra_chat_bloc.dart';
+import 'core/chat/extension_bloc.dart';
 import 'firebase_options.dart';
 import 'router.dart';
 
 void main() async {
   WidgetsFlutterBinding.ensureInitialized();
   await Firebase.initializeApp(options: DefaultFirebaseOptions.currentPlatform);
+
+  final messaging = FirebaseMessaging.instance;
+  await messaging.requestPermission();
+
   runApp(const App());
 }
 
@@ -38,6 +45,18 @@ class _AppState extends State<App> with WidgetsBindingObserver {
     _router = buildRouter(_authBloc);
     _statusBloc = StatusBloc(apiClient: _apiClient);
     _chatRequestBloc = ChatRequestBloc(apiClient: _apiClient);
+    _registerFcmToken();
+  }
+
+  Future<void> _registerFcmToken() {
+    return _authBloc.stream.where((s) => s is AuthAuthenticated).first.then((_) async {
+      try {
+        final token = await FirebaseMessaging.instance.getToken();
+        if (token != null) {
+          await _apiClient.post('/api/shared/device-token', data: {'token': token});
+        }
+      } catch (_) {}
+    });
   }
 
   @override
@@ -66,6 +85,8 @@ class _AppState extends State<App> with WidgetsBindingObserver {
         BlocProvider.value(value: _authBloc),
         BlocProvider.value(value: _statusBloc),
         BlocProvider.value(value: _chatRequestBloc),
+        BlocProvider(create: (_) => MitraChatBloc(apiClient: _apiClient)),
+        BlocProvider(create: (_) => ExtensionBloc(apiClient: _apiClient)),
         RepositoryProvider.value(value: _apiClient),
       ],
       child: BlocListener<AuthBloc, AuthState>(