fix: replace backend with localhost in nginx ws block

nginx.conf

@@ -28,7 +28,7 @@ server {
 
     # WebSocket requests
     location /ws/ {
-        proxy_pass http://backend:8000/ws/;
+        proxy_pass http://localhost:8000/ws/;
         proxy_http_version 1.1;
         proxy_set_header Upgrade $http_upgrade;
         proxy_set_header Connection "Upgrade";