Postgres 18 mudou o layout do mount canônico — dados ficam em subdir por
major-version (18/main) pra suportar pg_upgrade --link sem boundary
issues. Ref: docker-library/postgres#1259.
Antes: container subia em loop com "in 18+, these Docker images are
configured to store database data in a format compatible with
pg_ctlcluster" e "there appears to be PostgreSQL data in:
/var/lib/postgresql/data (unused mount/volume)".
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>