Login form is briefly flashing

[rrrnld]

To reproduce:

1. Login
2. Open some link in the app, for example an album
3. Copy the url
4. Paste it into a new tab

Behavior:
Before being redirected you can briefly see the login form after the loading spinner.

Expected behavior:
The loading spinner should be the only thing we see.

[rrrnld]

This is because the app finishes the boot process after we have verified our credentials (or made sure there aren't any. The relevant code is here: https://github.com/heyarne/airsonic-ui/blob/727d4548718a96867d5eb9ecc9daff752518b6c4/src/cljs/airsonic_ui/subs.cljs#L5-L12

As soon as we have credentials, :events/logged-in is fired, which only then redirects, thus causing the flashing.