db:export silently depends on unset DATABASE_URL, only DATABASE_URL_DIRECT is populated

Flagged by db-pluto-cc during PLUTO-700 migration 109 apply 2026-08-16: pnpm db:export reads DATABASE_URL, which is empty in .env.local (only DATABASE_URL_DIRECT is populated). db-pluto-cc worked around it by supplying DATABASE_URL from the environment manually. Needs an owner to either populate DATABASE_URL correctly or repoint db:export at DATABASE_URL_DIRECT, or it will silently break for the next person who runs the export without the same environment setup.