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/features/home/home_screen.dart

@@ -3,6 +3,7 @@ import 'package:flutter_bloc/flutter_bloc.dart';
 import 'package:go_router/go_router.dart';
 import '../../core/auth/auth_bloc.dart';
 import '../../core/pairing/pairing_bloc.dart';
+import '../chat/widgets/pricing_bottom_sheet.dart';
 
 class HomeScreen extends StatelessWidget {
   const HomeScreen({super.key});
@@ -33,6 +34,10 @@ class HomeScreen extends StatelessWidget {
             appBar: AppBar(
               title: const Text('Halo Bestie'),
               actions: [
+                IconButton(
+                  icon: const Icon(Icons.history),
+                  onPressed: () => context.push('/chat/history'),
+                ),
                 IconButton(
                   icon: const Icon(Icons.logout),
                   onPressed: () => context.read<AuthBloc>().add(LogoutRequested()),
@@ -51,7 +56,7 @@ class HomeScreen extends StatelessWidget {
                       style: ElevatedButton.styleFrom(
                         padding: const EdgeInsets.symmetric(horizontal: 48, vertical: 16),
                       ),
-                      onPressed: () => context.read<PairingBloc>().add(RequestPairing()),
+                      onPressed: () => PricingBottomSheet.show(context),
                       child: const Text('Mulai Curhat', style: TextStyle(fontSize: 18)),
                     ),
                   ],