feat(mobile): Implement Keycloak WebView authentication with HTTP callback

- Replace flutter_appauth with custom WebView implementation to resolve deep link issues
- Add KeycloakWebViewAuthService with integrated WebView for seamless authentication
- Configure Android manifest for HTTP cleartext traffic support
- Add network security config for development environment (192.168.1.11)
- Update Keycloak client to use HTTP callback endpoint (http://192.168.1.11:8080/auth/callback)
- Remove obsolete keycloak_auth_service.dart and temporary scripts
- Clean up dependencies and regenerate injection configuration
- Tested successfully on multiple Android devices (Xiaomi 2201116TG, SM A725F)

BREAKING CHANGE: Authentication flow now uses WebView instead of external browser
- Users will see Keycloak login page within the app instead of browser redirect
- Resolves ERR_CLEARTEXT_NOT_PERMITTED and deep link state management issues
- Maintains full OIDC compliance with PKCE flow and secure token storage

Technical improvements:
- WebView with custom navigation delegate for callback handling
- Automatic token extraction and user info parsing from JWT
- Proper error handling and user feedback
- Consistent authentication state management across app lifecycle

unionflow-mobile-apps/lib/features/navigation/presentation/pages/main_navigation.dart

@@ -6,6 +6,7 @@ import '../../../../shared/widgets/buttons/buttons.dart';
 import '../../../dashboard/presentation/pages/dashboard_page.dart';
 import '../../../members/presentation/pages/membres_list_page.dart';
 import '../../../cotisations/presentation/pages/cotisations_list_page.dart';
+import '../../../evenements/presentation/pages/evenements_page.dart';
 import '../widgets/custom_bottom_nav_bar.dart';
 
 class MainNavigation extends StatefulWidget {
@@ -105,7 +106,8 @@ class _MainNavigationState extends State<MainNavigation>
 
   Widget _buildFloatingActionButton() {
     // Afficher le FAB seulement sur certains onglets
-    if (_currentIndex == 1 || _currentIndex == 2 || _currentIndex == 3) {
+    // IMPORTANT: L'onglet Membres (index 1) a son propre FAB, donc on ne l'affiche pas ici
+    if (_currentIndex == 2 || _currentIndex == 3) {
       return ScaleTransition(
         scale: _fabAnimation,
         child: QuickButtons.fab(
@@ -212,20 +214,7 @@ class _MainNavigationState extends State<MainNavigation>
   }
 
   Widget _buildEventsPage() {
-    return const ComingSoonPage(
-      title: 'Module Événements',
-      description: 'Organisation et gestion d\'événements avec calendrier intégré',
-      icon: Icons.event_rounded,
-      color: AppTheme.warningColor,
-      features: [
-        'Calendrier interactif des événements',
-        'Gestion des inscriptions en ligne',
-        'Envoi d\'invitations automatiques',
-        'Suivi de la participation',
-        'Gestion des lieux et ressources',
-        'Sondages et feedback post-événement',
-      ],
-    );
+    return const EvenementsPage();
   }
 
   Widget _buildMorePage() {