Everything lives in the postgres-data volume and in deploy/.env. Without that .env file the database cannot be opened again.
One simple approach is a nightly compressed dump that overwrites the previous one. Add this line with crontab -e, and change the folder:
0 3 * * * cd /home/you/reloop/deploy && docker compose exec -T postgres pg_dump -U reloop reloop | gzip > /home/you/reloop-backup.sql.gzCopy the dump and deploy/.env to a second machine from time to time. Make an extra dump before every update.