feat(ui): HDMI refresh boost in the app, off only

The app gets its texts and the same rules as the menu: unticking Steam
Machine support or the kernel pin unticks it. It can't be turned on from
the app, as each step needs someone at the keyboard to confirm the picture.

lib/backend.sh

@@ -144,6 +144,8 @@ backend_apply() {
     [[ "${WANTED[gaming]:-0}" == 0 ]] && { WANTED[single]=0; WANTED[boot]=0; }
     [[ "${WANTED[kpin]:-0}" == 1 ]] && WANTED[machine]=1
     [[ "${WANTED[machine]:-0}" == 0 ]] && WANTED[kpin]=0
+    [[ "${WANTED[hdmi]:-0}" == 1 ]] && { WANTED[machine]=1; WANTED[kpin]=1; }
+    [[ "${WANTED[kpin]:-0}" == 0 ]] && WANTED[hdmi]=0
     case "$boot" in desktop) WANTED[boot]=1; WANTED[gaming]=1 ;; gamescope) WANTED[boot]=0 ;; esac
 
     REAPPLY=$reapply