Admin wiki page: an "Offsite copies" subsection under Backup and restore documenting the nightly restic snapshots to Scaleway, the append-only key on bay1 versus the removing key on the operator's machine, and the procedure to take one repository out of every snapshot (restic rewrite --forget with every on-disk name the repository has had, then prune, then find to confirm). The admin mr prune paragraph now points at it.
Ref #227