Stop web/scraper containers from using a stray literal DATABASE_URL in the
root .env (which desynced the postgres role password and caused persistent
'password authentication failed' errors). DATABASE_URL is now always computed
from POSTGRES_USER/POSTGRES_PASSWORD.
Also harden postgres-entrypoint.sh: log to stderr, retry on failure, and run
ALTER ROLE unconditionally so the stored password always matches the env.
