the migrated data has no literal 'admin' account — HAL's real admin login
is a personal account (jochens), not a generic one. Resetting that would
touch a real user's own credential, so the module gets its own dedicated
admin-group service account instead, same pattern as the minio per-module
service accounts. mesh-admin was created once by hand on novox to match
this manifest for the already-migrated data; a genuinely fresh install
seeds it automatically via NEXTCLOUD_ADMIN_USER/NEXTCLOUD_ADMIN_PASSWORD.