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/services/index.ts

@@ -6,4 +6,5 @@ export { analyticsService } from './analytics.service';
 export { archiveService } from './archive.service';
 export { emailService } from './email.service';
 export { settingsService } from './settings.service';
-export { cmsService } from './cms.service';
+export { cmsService } from './cms.service';
+export { notificationsService } from './notifications.service';