feat(core): refonte architecture transverse (cache, network, websocket, DI)

- lib/app : app.dart, router mis à jour (routes nouveaux modules)
- lib/core/cache : cache_service + cached_datasource_decorator
- lib/core/network : api_client, offline_manager, retry_policy
- lib/core/websocket : websocket service (reconnexion exponentielle, heartbeat)
- lib/core/di : injection + register_module
- lib/core/storage : pending_operations_store (offline support)
- lib/core/navigation : main_navigation_layout (onglets par rôle)
- lib/core/config : environment, lcb_ft_constants
- lib/core/utils : error_formatter, validators
- pubspec.yaml/lock : dépendances mises à jour

lib/app/router/app_router.dart

@@ -20,7 +20,7 @@ import '../../features/adhesions/presentation/pages/adhesions_page_wrapper.dart'
 import '../../features/settings/presentation/pages/system_settings_page.dart';
 import '../../features/dashboard/presentation/pages/advanced_dashboard_page.dart';
 import '../../features/admin/presentation/pages/user_management_page.dart';
-import '../../features/communication/presentation/pages/conversations_page.dart';
+import '../../features/communication/presentation/pages/conversations_page_wrapper.dart';
 import '../../features/finance_workflow/presentation/pages/pending_approvals_page.dart';
 import '../../features/finance_workflow/presentation/pages/budgets_list_page.dart';
 import '../../core/navigation/main_navigation_layout.dart';
@@ -86,7 +86,7 @@ class AppRouter {
     '/reports': (context) => const ReportsPageWrapper(),
     '/finances': (context) => const CotisationsPageWrapper(),
     '/adhesions': (context) => const AdhesionsPageWrapper(),
-    '/messages': (context) => const ConversationsPage(),
+    '/messages': (context) => const ConversationsPageWrapper(),
     '/settings': (context) => const SystemSettingsPage(),
     '/analytics': (context) {
       final authState = context.read<AuthBloc>().state;