The previous recipe backed the DB up as a mysqldump --tab into /var/lib/mysql-files with NO restore
hook (and the mysql data volume itself was not backupbot-labelled), so a restored backup silently
kept the live, un-restored DB state — data loss on restore. Add mysql_backup.sh (backup: gzipped
mysqldump --databases ghost into the data volume; restore: reimport it) wired via backupbot
backup.pre-hook + restore.post-hook, mirroring the postgres recipes (mattermost-lts, immich). Bump
1.2.0 -> 1.3.0.
