kuma-maintenance.py (open/list/delete, single-strategy windows,
version-tolerant addMaintenance probing) + pve-snapshot.sh rollback
opens a 30m window before touching a VM when ~/.creds/uptime-kuma.env
exists. TZ pinned America/Chicago. Verified: open->list(active=True)->
delete live on the fleet Kuma.
https://projects.knownelement.com/issues/769#note-4152