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/members/presentation/widgets/stats_grid_card.dart

@@ -147,7 +147,7 @@ class _StatsGridCardState extends State<StatsGridCard>
 
   Widget _buildStatCard(_StatItem item) {
     return Container(
-      padding: EdgeInsets.all(DesignSystem.spacingMd),
+      padding: const EdgeInsets.all(DesignSystem.spacingMd),
       decoration: BoxDecoration(
         color: AppTheme.surfaceLight,
         borderRadius: BorderRadius.circular(DesignSystem.radiusLg),
@@ -164,7 +164,7 @@ class _StatsGridCardState extends State<StatsGridCard>
             mainAxisAlignment: MainAxisAlignment.spaceBetween,
             children: [
               Container(
-                padding: EdgeInsets.all(DesignSystem.spacingSm),
+                padding: const EdgeInsets.all(DesignSystem.spacingSm),
                 decoration: BoxDecoration(
                   color: item.color.withOpacity(0.1),
                   borderRadius: BorderRadius.circular(DesignSystem.radiusMd),
@@ -176,7 +176,7 @@ class _StatsGridCardState extends State<StatsGridCard>
                 ),
               ),
               Container(
-                padding: EdgeInsets.symmetric(
+                padding: const EdgeInsets.symmetric(
                   horizontal: DesignSystem.spacingXs,
                   vertical: 2,
                 ),
@@ -199,7 +199,7 @@ class _StatsGridCardState extends State<StatsGridCard>
               ),
             ],
           ),
-          SizedBox(height: DesignSystem.spacingSm),
+          const SizedBox(height: DesignSystem.spacingSm),
           Text(
             item.value,
             style: DesignSystem.headlineMedium.copyWith(
@@ -207,7 +207,7 @@ class _StatsGridCardState extends State<StatsGridCard>
               color: AppTheme.textPrimary,
             ),
           ),
-          SizedBox(height: DesignSystem.spacingXs),
+          const SizedBox(height: DesignSystem.spacingXs),
           Text(
             item.title,
             style: DesignSystem.labelMedium.copyWith(