Add a host detail action that scans the target SSH host key with
ssh-keyscan and stores it on the selected SSH credential.
Merge scanned known_hosts entries without duplicates and let the
existing runtime config pass them through as UserKnownHostsFile for
unattended rsync over SSH.
Extend host checks to warn when the selected credential has no known_hosts
entries, making host key verification failures actionable from Django.
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.
