Android 3.30.8 auto-upload custom folder

### ⚠️ 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. Go to Settings -> Automatic upload
2. Create a new custom upload folder
3. Create a local file in the specified folder

### Expected behaviour

Upload this file to nextcloud

### Actual behaviour

file is not uploaded

### Android version

13

### Device brand and model

Google Pixel 4a

### Stock or custom OS?

Stock

### Nextcloud android app version

3.30.8

### Nextcloud server version

29.0.7

### Using a reverse proxy?

Yes

### Android logs

_No response_

### Server error logs

```bash

```

### Additional information

I know there are a lot of different threads about auto-upload in the Android client, especially 3.30.8 which broke a lot of stuff. But I didn’t find anything specific to my problem:

In December 2024 all my auto-upload stopped working, as did for probably everybody. I revoked all permissions from the app and granted them again. Now all media (fotos, videos, screenshots) are uploaded again.
But I also use one custom folder to upload my signal backups to nextcloud and I just can’t get this one working with this version. It is located directly in the internal storage (/storage/emulated/0/SignalBackups) and the nextcloud app just seems to see no files in this folder. I guess this is a permission problem somehow too?

What I tried:

- As I already said: I revoked all permissions and granted them again
- Under Andoid system settings → accounts → my nc account: I enabled file synchonization
- I can’t find nextcloud in Android system settings → apps → special app-access → access all files (some posts recommended to enable this for nextcloud, but it seems the app does not request this permission)
- I deleted the app completly and reinstalled everything from Play Store