Allow to copy the linkdevice URI

Description

When using signal-cli as main "device", linking Flare would happen through signal-cli addDevice --uri sgnl://…. Currently one would need to make a screenshot and run zbarimg to extract the URI. I suggest to show the URI to be copied as text or have a button that places it into the clipboard.

Additional information

Installation method: Flatpak

Version: 0.4.0

Additional information: I haven't linked Flare as device yet but I guess it should work