kamal-backup: Scheduled Rails Backups for Kamal Apps

kamal-backup is two pieces: a Ruby gem you add to your Rails app, and a Docker image you boot as a Kamal accessory. They point at a restic repository you bring yourself. The gem is your CLI. Local commands run directly on your machine using restic. Production-side commands shell out through Kamal into the accessory. The same kamal-backup binary covers setup (init, validate), on-demand operations (backup, list, check), data movement (restore local, restore production), verification (drill local, drill production), and audit (evidence). The Docker image (ghcr.io/crmne/kamal-backup) ships with restic, pg_dump, mariadb-dump/mysqldump, and sqlite3 baked in. The default container command is kamal-backup schedule, a loop that fires every backup_schedule_seconds and writes one database snapshot and one Active Storage file snapshot per run.