Move the mysqldump/gunzip commands directly into the
backupbot.backup.pre-hook / backupbot.restore.post-hook label values
on the db service and delete the external mysql_backup.sh + its
config mount + MYSQL_BACKUP_VERSION. Matches the inline pattern used
by akaunting / engelsystem / forgejo and removes one file from the
recipe surface area.
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.
