fix: 修复 Nginx 静态文件配置，优先使用本地文件

frontend/nginx.conf

@@ -28,6 +28,11 @@ server {
     }
 
     location /static {
+        # Try local static files first, then proxy to backend
+        try_files $uri $uri/ @backend_static;
+    }
+
+    location @backend_static {
         proxy_pass http://backend:8000;
     }