Phase 3.1: Complete mitra_app Riverpod migration (all blocs, fix auth bug)

- Migrate AuthBloc → MitraAuthNotifier (fixes stuck-loading bug: now returns
  MitraAuthInitialData when currentUser is null)
- Migrate StatusBloc → OnlineStatusNotifier (heartbeat timer + lifecycle)
- Migrate ExtensionBloc → MitraExtensionNotifier (accept/reject + goodbye)
- Migrate ChatRequestBloc → ChatRequestNotifier (WebSocket incoming requests)
- Migrate MitraChatBloc → MitraChatNotifier (WebSocket chat + messages)
- Update router to use Riverpod auth state for redirects
- Remove all flutter_bloc usage from mitra_app screens and main.dart
- MultiBlocProvider fully removed from mitra_app

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

mitra_app/lib/features/chat/widgets/incoming_request_sheet.dart

@@ -1,13 +1,13 @@
 import 'package:flutter/material.dart';
-import 'package:flutter_bloc/flutter_bloc.dart';
-import '../../../core/chat/chat_request_bloc.dart';
+import 'package:flutter_riverpod/flutter_riverpod.dart';
+import '../../../core/chat/chat_request_notifier.dart';
 
-class IncomingRequestSheet extends StatelessWidget {
+class IncomingRequestSheet extends ConsumerWidget {
   final String sessionId;
   const IncomingRequestSheet({super.key, required this.sessionId});
 
   @override
-  Widget build(BuildContext context) {
+  Widget build(BuildContext context, WidgetRef ref) {
     return Container(
       padding: const EdgeInsets.all(24),
       child: Column(
@@ -30,7 +30,7 @@ class IncomingRequestSheet extends StatelessWidget {
               Expanded(
                 child: OutlinedButton(
                   onPressed: () {
-                    context.read<ChatRequestBloc>().add(DeclineRequest(sessionId));
+                    ref.read(chatRequestProvider.notifier).decline(sessionId);
                     Navigator.of(context).pop();
                   },
                   child: const Text('Tolak'),
@@ -40,7 +40,7 @@ class IncomingRequestSheet extends StatelessWidget {
               Expanded(
                 child: ElevatedButton(
                   onPressed: () {
-                    context.read<ChatRequestBloc>().add(AcceptRequest(sessionId));
+                    ref.read(chatRequestProvider.notifier).accept(sessionId);
                     Navigator.of(context).pop();
                   },
                   child: const Text('Terima'),