Add filesystem-backed SSH credentials for the native systemd deployment
path. Generated keys are stored below POBSYNC_HOME with 0600
permissions, while Django keeps the public key, fingerprint, path, and
selection metadata.
Add a Django SSH key generation view, delete action for unused generated
keys, and a management command used by the installer to ensure a default
backup key exists.
Update runtime config to use generated key paths directly as IdentityFile,
extend host checks to verify key readability, and keep legacy uploaded
keys available for compatibility.
Add host-level checks for address, enabled state, SSH credential
selection, and backup directory readiness, and show them on the host
detail page.
Create host backup directories during host creation and prefill new
hosts from the default global config.
Add a staff-only logs view backed by journalctl with filtering by
pobsync unit, priority, and message text.
Improve runtime checks for gunicorn in virtualenv installs and ensure
the native installer grants the service user access to the backup root.
