Elegantly handle launching the app without wifi

[mrhappyasthma]

Currently launching without wifi shows a download error (from trying to fetch the latest update version) and then loads the full interface.

Ideally we should show a different landing page that mentions that the user is not connected to wifi.

Super ideally, provide an interface for users to connect to wifi directly within the updater app. (Although idk if this is feasible.)

[mynery]

I'd wish for more: If you are offline but find an atmosphere zip file, just take that one instead of trying to download it.