fix: resolve frontend API routing issues for Traefik deployment

Major fixes for production deployment with Traefik:

1. API Path Fixes:
   - Remove double /api prefix from all frontend service calls
   - Fix auth.service.ts to use correct paths (/auth/admin/login)
   - Update all services to use single /api prefix from base URL
   - Fix template literal paths in photo services

2. Docker Configuration:
   - Add build args for VITE_API_URL in docker-compose.prod.yml
   - Create Dockerfile.prod with proper API URL configuration
   - Ensure frontend is built with correct API base path

3. Documentation:
   - Add comprehensive TRAEFIK_DEPLOYMENT.md guide
   - Document proper Traefik labels and routing configuration
   - Include troubleshooting steps for common issues
   - Explain network configuration and SSL handling

This resolves:
- 502 Bad Gateway errors
- Double /api/api paths in requests
- Frontend unable to communicate with backend
- Login functionality not working

The frontend now correctly calls the backend API through Traefik's
routing, with all requests going to /api/* being forwarded to the
backend service on port 3000.

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

Co-Authored-By: Claude <noreply@anthropic.com>

frontend/src/services/categories.service.ts

@@ -19,30 +19,30 @@ export interface CreateCategoryData {
 export const categoriesService = {
   // Get all global categories
   async getGlobalCategories(): Promise<PhotoCategory[]> {
-    const response = await api.get<PhotoCategory[]>('/api/admin/categories/global');
+    const response = await api.get<PhotoCategory[]>('/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/${eventId}`);
+    const response = await api.get<PhotoCategory[]>(`/admin/categories/event/${eventId}`);
     return response.data;
   },
 
   // Create a new category
   async createCategory(data: CreateCategoryData): Promise<PhotoCategory> {
-    const response = await api.post<PhotoCategory>('/api/admin/categories', data);
+    const response = await api.post<PhotoCategory>('/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/${id}`, { name });
+    const response = await api.put<PhotoCategory>(`/admin/categories/${id}`, { name });
     return response.data;
   },
 
   // Delete a category
   async deleteCategory(id: number): Promise<void> {
-    await api.delete(`/api/admin/categories/${id}`);
+    await api.delete(`/admin/categories/${id}`);
   }
 };