.backups folder may not be obvious to user and consumes disk space

**Link to original comment:** https://github.com/beyond-all-reason/BAR-Devtools/pull/33#discussion_r3367980676

Given that the .backups folder now has 23 GB of stuff in it... maybe we want a "just backup::purge" option surfaced to the user so they can see disk consumption done by the backup and easily delete backups that they no longer need.