fix: nginx 管理后台改用 root 替代 alias 修复 JS MIME 类型错误

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

nginx.conf

@@ -11,7 +11,7 @@ server {
 
     # 管理后台前端
     location /admin/ {
-        alias /usr/share/nginx/admin/;
+        root /usr/share/nginx;
         try_files $uri $uri/ /admin/index.html;
         add_header Cache-Control "no-cache, no-store, must-revalidate";
     }