Carve MAINTENANCE_CREATE/UPDATE/DELETE out of the admin denylist so
HA automations can log "cleaned nozzle" / reset a counter via API key
without granting broader printer control. Follows the same shape as
can_manage_library and can_manage_inventory: new column, allowlist
entry, UI checkbox, wiki row, RBAC test coverage.
Distinct backfill: these perms were EXPLICITLY denied for every API
key before this change (no existing integration relies on them), so
existing rows migrate to FALSE — no silent scope widening on upgrade.
New keys default to TRUE, matching the safe-on-by-default pattern.
Bundled SpoolBuddy kiosk key gets False explicitly (kiosk doesn't need it).