Fix healthcheck: use 127.0.0.1 instead of localhost for Alpine compatibility

Alpine Linux resolves localhost to ::1 (IPv6), but nginx only listens on
IPv4. This caused healthchecks to fail, keeping the container in "starting"
state and preventing Traefik from creating a router.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Dockerfile

@@ -33,7 +33,7 @@ EXPOSE 80
 
 # Health check
 HEALTHCHECK --interval=30s --timeout=3s --start-period=5s --retries=3 \
-  CMD wget --quiet --tries=1 --spider http://localhost/ || exit 1
+  CMD wget --quiet --tries=1 --spider http://127.0.0.1/ || exit 1
 
 # Start nginx
 CMD ["nginx", "-g", "daemon off;"]