Migrating from Unifi UXG-Lite to Express 7

A UniFi restore that reports no errors, restarts cleanly, and lets you log in with your admin account, but somehow leaves you with an empty configuration, is a special kind of frustrating. That's the short version of what it took to move from a HostiFi-hosted controller to a local UniFi Express 7 (UX7). It should have been a cable swap and a restore. Instead it turned into a two-attempt debugging exercise, followed by a workaround involving a throwaway Docker controller and some direct MongoDB open-heart surgery.