Can't log out of a newly created account

### Steps to reproduce

1. Open a private window
2. Start a call as a new guest user
3. End the call
4. Go to the user menu > sign in > create an account
5. Create your account
6. Open the user menu again

### Outcome

#### What did you expect?

There should be a "log out" button.

#### What happened instead?

Instead there is still a "sign in" button. The app thinks I'm still a guest even though I have an account now.

If I'm remembering correctly, we were talking about removing the ability to sign in or create an account, and instead letting every user be a guest user. That would be the way of least resistance to fix this :)

### Operating system

NixOS unstable

### Browser information

Firefox 127

### URL for webapp

call.element.io

### Will you send logs?

No

Start by reproducing the guest-to-account flow in a private Firefox window at call.element.io, then trace how the user menu determines whether to show sign-in or log-out after account creation. Done means a newly created account is recognized as signed in and the user menu offers a log-out button.

Written by the indexing model from the issue text.