Hub suggests to register device, App shows "Access denied"

### Please agree to the following

- [X] I have searched [existing issues](https://github.com/cryptomator/hub/issues?q=) for duplicates
- [X] I agree to follow this project's [Code of Conduct](https://github.com/cryptomator/hub/blob/develop/.github/CODE_OF_CONDUCT.md)

### Summary

App unlock with a different user than the device register user, Hub says to register device, but is impossible in app.

### System Setup

```markdown
- Hub: 96582145661fb0a29ac36791e33e4bf02386593e
- Keycloak: 19.0.2
- Cryptomator (Desktop/Android/iOS): Desktop 1.6.15
```

### Steps to Reproduce

1. Create two users A and B
2. Register device with user A (during unlock)
3. logout A
4. unlock any other hub vault, login with B

### Expected Behavior

Message shown: Device registered for different user

### Actual Behavior

Opened webpage says to register device in app, app says "Access denied"

### Reproducibility

Always

### Relevant Log Output

_No response_

### Anything else?