Update contract-check-http.conf.template

deploy/nginx/templates/contract-check-http.conf.template

@@ -21,7 +21,10 @@ server {
     # IPv6 too — otherwise IPv6 clients fall through to nginx's stock
     # default.conf server (static /usr/share/nginx/html → 404s).
     listen [::]:80;
-    server_name ${NGINX_SERVER_NAME};
+    # `localhost` keeps the container healthcheck (Host: localhost) on this
+    # server instead of falling through to nginx's stock default.conf (404).
+    # conf.d loads contract-check.conf first, so this name wins the conflict.
+    server_name ${NGINX_SERVER_NAME} localhost;
 
     location ~ ^/(healthz|readyz|metrics|api/|admin/|docs|openapi.json) {
         proxy_pass http://api;