Add logo SVG asset and improve authentication error handling

- Added a new logo SVG asset to the AssetsManager for better branding.
- Updated the AuthViewModel to notify listeners on authentication error changes.
- Modified DesktopNavigationWidget to use the new logo SVG with specified dimensions for improved layout.

lib/view_models/auth_view_model.dart

@@ -84,6 +84,7 @@ class AuthViewModel with ChangeNotifier {
         break;
       case Error<LoginResponseModel>():
         _errorMessage = result.error.toString();
+        notifyListeners();
         break;
     }