nginx: auch auf IPv6 lauschen, Healthcheck über 127.0.0.1

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01WT5AWHW7UkHrBjhNyA2y8X

nginx.conf

@@ -1,5 +1,6 @@
 server {
     listen 80;
+    listen [::]:80;
     server_name _;
     root /usr/share/nginx/html;
     index index.html;