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.