Drop the Compose/Caddy example: production runs on Kubernetes, and locally
the container only needs a forwarded port and a volume. The README now gives
the `docker run` steps and what a Kubernetes deployment needs (one replica,
since it's a single SQLite file; a volume at /data; TLS at the ingress).
The server only shut down on Ctrl-C, so `docker stop` and pod termination,
which send SIGTERM, waited out the grace period and killed it. It now shuts
down gracefully on either.
Also ignore `.env`, which can hold the OIDC client secret.