Allow specifying transport+address for the server via CLI #3
Description
Right now you need to send a request to /connect when using the server and specify how to reach the printer.
The big benefit of the server compared to simply calling niimblue-cli print ... directly is that the client could be remote... from that point of view it makes little sense that the client needs to tell the server how to reach the printer. Instead, it should auto-connect on startup (and maybe reconnect when a disconnection is detected or when trying to print something), so one can just send a request to /print w/o having to care about connection state (no printer being reachable would simply be an error at print time).