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/pubspec.yaml

@@ -24,6 +24,8 @@ dependencies:
   jwt_decoder: ^2.0.1
   crypto: ^3.0.5
   shared_preferences: ^2.3.2
+  flutter_appauth: ^6.0.2
+  webview_flutter: ^4.4.2
 
   # HTTP
   pretty_dio_logger: ^1.4.0
@@ -43,7 +45,17 @@ dependencies:
   # Utils
   uuid: ^4.5.1
   url_launcher: ^6.3.1
+  permission_handler: ^11.3.1
   package_info_plus: ^8.0.2
+  flutter_staggered_animations: ^1.1.1
+
+  # Export/Import
+  excel: ^4.0.6
+  csv: ^6.0.0
+  pdf: ^3.11.1
+  path_provider: ^2.1.4
+  file_picker: ^8.1.2
+  share_plus: ^10.0.2
 
 dev_dependencies:
   flutter_test: