curl -sSI and Traefik probes use HEAD; the server only handled GET, causing HEAD / to fall through to the 404 handler.
Number guessing game (1-100, 7 attempts) as a HAL custom-app module. Serves HTML form UI with per-session state via cookie, no npm deps. Traefik labels for txt.${DOMAIN} on websecure with letsencrypt TLS.