File preview may leak private information

### ⚠️ 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

1. Have some private images in a folder on your Nextcloud account
2. Open the nextcloud app with a friend watching, to show some less private files
3. The friend gets to see a preview of the private images

### Expected behaviour

While it is overkill, implementing #14967 would allow this issue to be avoided by disabling recommendations entirely.
A better solution (but also more work) would be to allow the user to select folders which should be excluded from recommendations.

### Actual behaviour

The app shows the preview for everyone to see.

### Android version

15

### Device brand and model

Fairphone 5

### Stock or custom OS?

Stock

### Nextcloud android app version

34.1.1

### Nextcloud server version

Nextcloud Hub 26 Winter (AIO)

### Using a reverse proxy?

No

### Android logs

_No response_

### Server error logs

```bash

```

### Additional information

_No response_

Commencez par reproduire le problème avec des images privées et examinez le flux de recommandations et de prévisualisation des fichiers de l’application ; issue #14967 est la référence associée. La tâche sera terminée lorsque les prévisualisations des dossiers privés n’apparaîtront plus pour les autres utilisateurs, que les recommandations attendues seront conservées et que le comportement choisi d’exclusion des dossiers sera documenté et testé.

Rédigé par le modèle d'indexation à partir du texte de l'issue.