The custom tier runs on the PR head — now genuinely the official discourse/discourse image (prevb
stopped the overlay reverting it to bitnamilegacy). mint_admin hardcoded /opt/bitnami/discourse (404 on
official) → create-topic roundtrip failed. Detect /var/www/discourse, re-export DISCOURSE_DB_PASSWORD
from /run/secrets (entrypoint exports it only for boot), run bin/rails; keep bitnami fallback.
