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/services/categories.service.ts

@@ -0,0 +1,48 @@
+import { api } from '../config/api';
+
+export interface PhotoCategory {
+  id: number;
+  name: string;
+  slug: string;
+  is_global: boolean;
+  event_id: number | null;
+  created_at: string;
+}
+
+export interface CreateCategoryData {
+  name: string;
+  slug?: string;
+  is_global?: boolean;
+  event_id?: number;
+}
+
+export const categoriesService = {
+  // Get all global categories
+  async getGlobalCategories(): Promise<PhotoCategory[]> {
+    const response = await api.get<PhotoCategory[]>('/api/admin/categories/global');
+    return response.data;
+  },
+
+  // Get categories for a specific event (global + event-specific)
+  async getEventCategories(eventId: number): Promise<PhotoCategory[]> {
+    const response = await api.get<PhotoCategory[]>(`/api/admin/categories/event/${eventId}`);
+    return response.data;
+  },
+
+  // Create a new category
+  async createCategory(data: CreateCategoryData): Promise<PhotoCategory> {
+    const response = await api.post<PhotoCategory>('/api/admin/categories', data);
+    return response.data;
+  },
+
+  // Update a category
+  async updateCategory(id: number, name: string): Promise<PhotoCategory> {
+    const response = await api.put<PhotoCategory>(`/api/admin/categories/${id}`, { name });
+    return response.data;
+  },
+
+  // Delete a category
+  async deleteCategory(id: number): Promise<void> {
+    await api.delete(`/api/admin/categories/${id}`);
+  }
+};