Warn user when not connected to Wi-Fi during onboarding

[SeanPM5]

Is your feature request related to a problem? Please describe.

During onboarding, if you're on cellular and attempt to connect to a local IP it will give you a vague "request timed out" error message. See #734

Describe the solution you'd like
These scenarios should be caught and handled better. There should either be a warning ahead of time, or a more friendly error message.

I believe something like this is already done if you attempt onboarding with Airplane Mode enabled, so this would kind of be expanding upon that.

Describe alternatives you've considered

Additional context