AV - prevent app shutdown

[0xflux]

I think I should decouple um_engine from the Tauri app and use IPC to talk to um_engine, and run um_engine as svc which is difficult to kill, and to implement some kind of DACL for only SYSTEM being able to kill it. If the GUI shuts down, that's fine, but dont want the um_engine to shut down.

May require significant rearchitecting.