Path for local backups

[loudar]

Since the local backups are stored on the main disk (except if you have /data/coolify mounted to an external volume), which can be small - I'd love the option to specify a target folder for local backups (like an external volume).

Since local backups are already integrated, I think this should be on the simpler side of things, because it's one more (optional) config value for a backup and then using that when writing the backup .gz.