feat: disable user messaging and retain公益 service guidance

infrastructure/nginx-production.conf

@@ -147,16 +147,10 @@ http {
             proxy_read_timeout 60s;
         }
 
-        # WebSocket proxy
+        # 用户间即时聊天已下线，避免网关继续暴露 WebSocket 入口。
         location /ws/ {
-            limit_req zone=ws burst=20 nodelay;
-            proxy_pass http://backend;
-            proxy_http_version 1.1;
-            proxy_set_header Upgrade $http_upgrade;
-            proxy_set_header Connection "upgrade";
-            proxy_set_header Host $host;
-            proxy_set_header X-Real-IP $remote_addr;
-            proxy_read_timeout 3600s;
+            default_type application/json;
+            return 410 '{"success":false,"code":"CHAT_DISABLED","message":"平台未提供用户之间的即时聊天功能","data":null}';
         }
 
         # Auth endpoints (strict rate limiting)