Fix admin routes path for Traefik reverse proxy

Traefik strips the /api prefix before forwarding requests to the backend,
so /api/admin requests arrive as /admin. Changed route mounting from
/api/admin to /admin to match the actual incoming request path.

server.js

@@ -147,8 +147,8 @@ app.use('/auth', authRoutes);
 // Mount activity routes
 app.use('/activity', activityRoutes);
 
-// Mount admin routes
-app.use('/api/admin', adminRoutes);
+// Mount admin routes (Traefik strips /api prefix, so /api/admin becomes /admin)
+app.use('/admin', adminRoutes);
 
 // Health check endpoint
 app.get('/health', (req, res) => {