fix how to see if we need gui or voice and condition back button on backend selection page

[AIIX]

• can_use_gui() and is_gui_connected() always report false here, its better to check if is_gui_running() and can_use_touch_and_mouse() here this seems to work better.
• the check must not only be in init but also at runtime of when handle pairing is called, there is a chance that setup skill will be initialized much before gui has even started or connected, so lets do a double check here to determine the correct mode
• hide the back button to language select if language selection is actually disabled on the backend selection page