SQLite DB in the K8s pod is ephemeral (no PV). On pod restart,
migrate_from_json() re-reads the remote JSON files. Without syncing
back, any server/cert changes after migration would be lost.
Now every server/cert write to SQLite also writes the corresponding
JSON file to the remote host, keeping them in sync.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>