cups: add comprehensive CUPs setting page

- Add printers
- Delete printers
- Use polkit APIs as fallback on auth errors
- Fix ref system to conditionally subscribe to cups when wanted

core/cmd/dms/shell.go

@@ -383,6 +383,7 @@ func runShellDaemon(session bool) {
 				errChan <- fmt.Errorf("server panic: %v", r)
 			}
 		}()
+		server.CLIVersion = Version
 		if err := server.Start(false); err != nil {
 			errChan <- fmt.Errorf("server error: %w", err)
 		}