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/android/app/build.gradle

@@ -7,7 +7,7 @@ plugins {
 
 android {
     namespace = "dev.lions.unionflow_mobile_apps"
-    compileSdk = 34
+    compileSdk = 35
     ndkVersion = flutter.ndkVersion
 
     compileOptions {
@@ -28,6 +28,12 @@ android {
         targetSdk = flutter.targetSdkVersion
         versionCode = flutter.versionCode
         versionName = flutter.versionName
+
+        // Configuration pour flutter_appauth
+        manifestPlaceholders = [
+            'appAuthRedirectScheme': 'dev.lions.unionflow-mobile',
+            'applicationName': 'android.app.Application'
+        ]
     }
 
     buildTypes {