Add initial setup flow where required
This adds several new pages for "initial setup" in places where this is needed. In some cases, the environment does not have a password service so Tokodon refuses to continue in order to prevent logging in and losing your credentials. On Android, the notifications permission is prompted here too.
(The screenshots may be out of date)
In the ideal KDE Plasma desktop setup (or GNOME Desktop) there is no setup.
Fixes BUG: 477927 and BUG: 473787