Encryption passphrase regenerates when you switch apps

### ⚠️ Before posting ⚠️

- [X] This is a **bug**, not a question or an enhancement.
- [X] I've [searched for similar issues](https://github.com/nextcloud/android/issues) and didn't find a duplicate.
- [X] I've written a clear and descriptive title for this issue, not just "Bug" or "Crash".
- [X] I agree to follow Nextcloud's [Code of Conduct](https://nextcloud.com/contribute/code-of-conduct/).

### Steps to reproduce

When setting up encryption, the app creates and shows you a new passphrase. If you decide to copy the passphrase and then paste it into a password manager, then come back to the app, it will then create a new passphrase, different from the one you pasted into your password manager, leading to the encryption passphrase being lost.

### Expected behaviour

After the passphrase dialog appears, I would expect the passphrase to **not change** until I click cancel and then "set up encryption" again.

### Actual behaviour

Any time you switch apps and come back the passphrase gets recreated.

### Android version

10

### Device brand and model

Oneplus 6

### Stock or custom OS?

Stock

### Nextcloud android app version

3.24.2

### Nextcloud server version

26.0.1

### Using a reverse proxy?

Yes

### Android logs

Not using a beta version, but I don't think logs would be required for this issue.

### Server error logs

```bash
N/A
```

### Additional information

Screen recording: https://nextcloud.jordanle.es/s/PkcACNNecMifpkD

If the link doesn't work, then ping me and I'll fix it (I'm still fiddling with my Nextcloud instance so it might bork)