Phase 3 testing fixes: Fastify 5, SSE→WebSocket+FCM, enums, security, session lifecycle

- Upgrade Fastify 4→5 with all plugins (@fastify/websocket 11, cors 11, sensible 6)
- Migrate all SSE endpoints to WebSocket + FCM push (mitra chat requests, customer pairing status)
- Add flutter_local_notifications for foreground push notifications with sound
- Add splash screen to both apps (hide auth loading flash)
- Introduce constants/enums across entire codebase (no raw string literals)
- Move price tiers from hardcoded array to app_config DB (data-driven, includes 1-min test tier)
- Add session ownership validation on all shared chat routes
- Add ownership checks on endSession, respondToExtension, requestExtension
- Fix session timer: auto-complete expired/stale sessions on server restart
- Add 5-min grace period for abandoned closing sessions
- Fix extension flow: proper session_resumed handling, clearExtensionRequest, closure grace timer cleanup
- Fix chat screens: ConnectChat in initState, session status check on connect
- Fix customer expired view: 5-min countdown, closure state priority over expired state
- Fix mitra extension UI: loading spinner, disable buttons, handle EXTENSION_RESOLVED error
- Fix GoRouter navigation consistency (no more Navigator.pushNamed)
- Fix goodbye view keyboard overflow (SingleChildScrollView)
- Add active session card on customer home screen with refresh on navigate back
- Fix PricingBottomSheet extension mode (RequestExtension instead of new pairing)
- Send session_resumed to both parties on extension accept

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

mitra_app/lib/features/home/home_screen.dart

@@ -1,5 +1,6 @@
 import 'package:flutter/material.dart';
 import 'package:flutter_bloc/flutter_bloc.dart';
+import 'package:go_router/go_router.dart';
 import '../../core/auth/auth_bloc.dart';
 import '../../core/status/status_bloc.dart';
 import '../../core/chat/chat_request_bloc.dart';
@@ -65,9 +66,11 @@ class _HomeScreenState extends State<HomeScreen> with WidgetsBindingObserver {
             if (state is ChatRequestIncoming) {
               _showIncomingRequest(state.sessionId);
             } else if (state is ChatRequestAccepted) {
-              ScaffoldMessenger.of(context).showSnackBar(
-                const SnackBar(content: Text('Sesi baru diterima!')),
-              );
+              final session = state.session;
+              final sessionId = session['session_id'] as String? ?? session['id'] as String;
+              context.push('/chat/session/$sessionId', extra: {
+                'customerName': session['customer_display_name'] as String? ?? 'Customer',
+              });
             }
           },
         ),
@@ -177,7 +180,7 @@ class _ActiveSessionsButton extends StatelessWidget {
             leading: const Icon(Icons.chat_bubble_outline),
             title: const Text('Sesi Aktif'),
             trailing: const Icon(Icons.chevron_right),
-            onTap: () => Navigator.of(context).pushNamed('/sessions'),
+            onTap: () => context.push('/sessions'),
           ),
         ),
         Card(
@@ -185,7 +188,7 @@ class _ActiveSessionsButton extends StatelessWidget {
             leading: const Icon(Icons.history),
             title: const Text('Riwayat Chat'),
             trailing: const Icon(Icons.chevron_right),
-            onTap: () => Navigator.of(context).pushNamed('/chat/history'),
+            onTap: () => context.push('/chat/history'),
           ),
         ),
       ],