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 <noreply@anthropic.com>

backend/src/routes/admin.js

@@ -10,6 +10,7 @@ const eventsRoutes = require('./adminEvents');
 const photosRoutes = require('./adminPhotos');
 const categoriesRoutes = require('./adminCategories');
 const cmsRoutes = require('./adminCMS');
+const notificationsRoutes = require('./adminNotifications');
 
 // Mount sub-routers
 router.use('/dashboard', dashboardRoutes);
@@ -20,5 +21,6 @@ router.use('/events', eventsRoutes);
 router.use('/events', photosRoutes);
 router.use('/categories', categoriesRoutes);
 router.use('/cms', cmsRoutes);
+router.use('/notifications', notificationsRoutes);
 
 module.exports = router;