Fix PostgreSQL not listening on the internal network

[xrhstosmour]

What:

1. Sets listen_addresses = '*' in databases/postgresql/configuration/postgresql.conf. Without it, Postgres only binds to localhost inside its own container and refuses connections from any other container on the shared internal network, including its existing consumers in separate compose projects (GlitchTip, Metabase, pgAdmin4).
2. To keep this from expanding exposure, also restricts the published host port to 127.0.0.1 in docker-compose.yml, the same restriction already applied to pgAdmin4/Metabase/Redis Commander/Mailpit. Other containers reach Postgres over the internal Docker network directly, never through the published host port, so this only affects local/tunnelled admin access, not container-to-container connectivity.

Why:

Found while wiring Authelia to the shared postgresql container in #52: a plain nc from an unrelated container on the internal network got connection refused, confirmed to be listen_addresses defaulting to localhost rather than a credentials or networking issue.

Testing:

1. docker compose config validates with no errors, docker port confirms the host binding is 127.0.0.1:5432, not 0.0.0.0:5432.
2. SHOW listen_addresses; returns * after the fix.
3. Confirmed both paths work: nc from the host to 127.0.0.1:5432 succeeds, and nc from an unrelated container on the internal network to postgresql:5432 also succeeds.
4. docker compose down -v cleans up with no leftover state.