Another idea for running the server in the background would be to use Systemd Socket Activation, this way the Server would autostart if it is needed (=if a Request comes in), and could stop after a certain time of idle.
This way it would not be neccessary to waste resources if nothing is using the server, but activation would be transparent to any client app.
This would of corse imply that some proper IPC Mechanism is in place, because I don't think the "stop/start when GUI is launched" would work too well with that