Fix brand theme application and add comprehensive translations

- Fixed theme not being reflected on gallery and admin login pages
- Created GlobalThemeProvider to apply themes globally
- Updated gallery and admin login pages to use dynamic CSS variables
- Added complete translations for all admin sections in English and German:
  - Notifications management
  - Event view and creation
  - Photo upload functionality
  - Category management
  - Archive page view
  - Analytics dashboard
  - Branding and theme settings
  - System settings
  - CMS page management
  - Email configuration
- Fixed admin photo management display issues
- Fixed photo upload category assignment
- Added password reset functionality for galleries
- Improved error handling and user feedback

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <[email protected]>

frontend/src/components/common/AuthenticatedImage.tsx

@@ -54,8 +54,12 @@ export const AuthenticatedImage: React.FC<AuthenticatedImageProps> = ({
           }
         }
         
-        console.log('Fetching authenticated image:', imageUrl);
-        const response = await fetch(imageUrl, {
+        // Prepend API URL for absolute paths
+        const apiUrl = import.meta.env.VITE_API_URL || 'http://localhost:3001';
+        const fullImageUrl = imageUrl.startsWith('/') ? `${apiUrl}${imageUrl}` : imageUrl;
+        
+        console.log('Fetching authenticated image:', fullImageUrl);
+        const response = await fetch(fullImageUrl, {
           headers: {
             'Authorization': `Bearer ${token}`
           }