Fix styling of log out screen

[roundhill]

When you log out of the web app, you get this:

Expected

A nice looking log out view. Let's make the text work for any theme, and maybe center it in the view better. It could maybe animate a bit too?

Observed

Dark text on dark bg (I'm in dark mode obviously!)

Reproduced

1. Sign in to the web app
2. Sign out from Settings
3. You'll briefly see the not-so-great log out view