Fix styling of log out screen

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

Start by reproducing the logout flow from Settings and locate the view shown during sign-out. Inspect how its text and theme styles are applied, then adjust the view so the message remains readable and is better centered across themes. Done means the logout view no longer shows dark text on a dark background and presents the expected improved layout.

Written by the indexing model from the issue text.