purge old bacula catalogs on host retirement
If I go into the bacula console now (`bconsole`) and look at the restore menu (`restore` then `5`), I see this:
```
Select item: (1-13): 5
Defined Clients:
1: alberti.torproject.org-fd
2: archeotrichon.torproject.org-fd
3: archive-01.torproject.org-fd
4: arlgirdense.torproject.org-fd
5: aroides.torproject.org-fd
6: bacula-director-01.torproject.org-fd
7: bahri.torproject.org-fd
8: bracteata.torproject.org-fd
9: brandegei.torproject.org-fd
10: brulloi.torproject.org-fd
11: build-arm-01.torproject.org-fd
[...]
166: web-hetzner-01.torproject.org-fd
167: wendelboi.torproject.org-fd
168: weschniakowii.torproject.org-fd
169: yatei.torproject.org-fd
```
ie. a *lot* more hosts than what we actually have running right now. some have been gone for so long I don't think they were around when I arrived, two years ago.
Clearly, the catalog never gets purged. This was first identified in #30880 (e.g. https://gitlab.torproject.org/tpo/tpa/team/-/issues/30880#note_2541504), but never really fixed. Now that the director is at 90% disk again, it might be time to look into this.
issue