PRIVATE_PORT optional for docker compose port

[maxproske]

Related issue

Closes #11859, and continues #11874 which was approved but went stale.

AI Disclaimer: Claude Code helped sharpen after I incorporated all requested changes from the stale PR.

What I did

Align docker compose port closer with docker port. When no port given, list all mappings.

Future improvement: allow inline protocol like docker port does (eg. 80/udp)?

# --- Before ---
docker compose port web
# "port" requires at least 2 arguments

# --- After ---
docker compose port web
# 80/tcp -> 0.0.0.0:8080
# 443/tcp -> 0.0.0.0:8443
# 53/udp -> 0.0.0.0:5353

docker compose port web 80
# 0.0.0.0:8080