feat: update login, event detail, theme, and API client

- Improved event detail page with carousel, map, and layout fixes
- Updated login screen with video background and glassmorphism
- API client development mode with mock responses
- Theme manager and main app updates

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

lib/core/api/api_client.dart

@@ -6,6 +6,8 @@ import '../storage/token_storage.dart';
 
 class ApiClient {
   static const Duration _timeout = Duration(seconds: 30);
+  // Set to true to enable mock/offline development mode (useful when backend is unavailable)
+  static const bool _developmentMode = true;
 
   /// POST request
   ///
@@ -34,6 +36,30 @@ class ApiClient {
           .timeout(_timeout);
     } catch (e) {
       if (kDebugMode) debugPrint('ApiClient.post network error: $e');
+
+      // Development mode: return mock responses for common endpoints on network errors
+      if (_developmentMode) {
+        if (url.contains('/user/login/')) {
+          if (kDebugMode) debugPrint('Development mode: returning mock login response');
+          final email = finalBody['username'] ?? 'test@example.com';
+          return {
+            'token': 'mock_token_${DateTime.now().millisecondsSinceEpoch}',
+            'username': email,
+            'email': email,
+            'phone_number': '+1234567890',
+          };
+        } else if (url.contains('/user/register/')) {
+          if (kDebugMode) debugPrint('Development mode: returning mock register response');
+          final email = finalBody['email'] ?? 'test@example.com';
+          return {
+            'token': 'mock_token_${DateTime.now().millisecondsSinceEpoch}',
+            'username': email,
+            'email': email,
+            'phone_number': finalBody['phone_number'] ?? '+1234567890',
+          };
+        }
+      }
+
       throw Exception('Network error: $e');
     }