Fix language setting not being saved to database on admin settings page

- Added default_language field to general settings state in SettingsPage
- Replaced LanguageSelector component with simple select dropdown on settings page
- Fixed public settings endpoint to read general_default_language from database
- Language setting now properly saved when clicking Save Settings button
- Setting is correctly used by gallery login page and legal pages

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

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

frontend/src/pages/admin/EventDetailsPage.tsx

@@ -20,7 +20,7 @@ import { format, parseISO, differenceInDays } from 'date-fns';
 import { toast } from 'react-toastify';
 
 import { Button, Input, Card, Loading } from '../../components/common';
-import { PhotoUpload } from '../../components/admin';
+import { PhotoUpload, EventCategoryManager } from '../../components/admin';
 import { useQuery, useMutation, useQueryClient } from '@tanstack/react-query';
 import { eventsService } from '../../services/events.service';
 import { galleryService } from '../../services/gallery.service';
@@ -408,10 +408,14 @@ export const EventDetailsPage: React.FC = () => {
                   <strong>Storage Location:</strong> /storage/events/active/{event.slug}/
                 </p>
                 <p className="text-xs text-blue-600 mt-1">
-                  Photos can also be added by placing them in the 'individual' or 'collages' folders.
+                  Photos are organized by categories you define.
                 </p>
               </div>
             </div>
+            
+            <div className="mt-6 pt-4 border-t border-neutral-200">
+              <EventCategoryManager eventId={parseInt(id!)} />
+            </div>
           </Card>
 
           {/* Actions */}