Pair a device from Settings
Settings, Your phone now shows the local server, a pairing code with a five minute countdown, and every paired device with a remove button.
The app now starts its local server by itself, next to the engine, and stops it when you quit. Nothing to set up.
Open Settings, then Your phone. Pair a device shows a code read in groups of four and a bar counting down five minutes. The device appears in the list as soon as it uses the code.
A paired device keeps working until you remove it. Remove is one click, and its key stops working at once.
For now the server answers on this Mac only. Reaching it from your phone over your home network comes next.