feat(nginx): enhance WebSocket support in demo configuration with proxy settings

nginx.demo.conf

@@ -203,6 +203,16 @@ server {
     }
 
     location /ws {
+        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_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
+        proxy_set_header X-Forwarded-Proto $scheme;
+
+        # In demo mode, there is no WebSocket backend service.
+        # This block is configured to support WSS upgrades from a reverse proxy.
         return 503;
     }