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/core/auth/presentation/auth_wrapper.dart

@@ -0,0 +1,59 @@
+import 'package:flutter/material.dart';
+import '../../../features/auth/presentation/pages/keycloak_login_page.dart';
+import '../../../features/navigation/presentation/pages/main_navigation.dart';
+import '../services/keycloak_webview_auth_service.dart';
+import '../models/auth_state.dart';
+import '../../di/injection.dart';
+
+/// Wrapper qui gère l'authentification et le routage
+class AuthWrapper extends StatefulWidget {
+  const AuthWrapper({super.key});
+
+  @override
+  State<AuthWrapper> createState() => _AuthWrapperState();
+}
+
+class _AuthWrapperState extends State<AuthWrapper> {
+  late KeycloakWebViewAuthService _authService;
+
+  @override
+  void initState() {
+    super.initState();
+    _authService = getIt<KeycloakWebViewAuthService>();
+  }
+
+  @override
+  Widget build(BuildContext context) {
+    return StreamBuilder<AuthState>(
+      stream: _authService.authStateStream,
+      initialData: _authService.currentState,
+      builder: (context, snapshot) {
+        final authState = snapshot.data ?? const AuthState.unknown();
+
+        // Affichage de l'écran de chargement pendant la vérification
+        if (authState.isChecking) {
+          return const Scaffold(
+            body: Center(
+              child: Column(
+                mainAxisAlignment: MainAxisAlignment.center,
+                children: [
+                  CircularProgressIndicator(),
+                  SizedBox(height: 16),
+                  Text('Vérification de l\'authentification...'),
+                ],
+              ),
+            ),
+          );
+        }
+
+        // Si l'utilisateur est authentifié, afficher l'application principale
+        if (authState.isAuthenticated) {
+          return const MainNavigation();
+        }
+
+        // Sinon, afficher la page de connexion
+        return const KeycloakLoginPage();
+      },
+    );
+  }
+}