upload changes case of file extension to lowercase

### ⚠️ 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. navigate to a folder that you can uploada file
2. select a file to upload
3. goto upload screen (paused). FILE.JPG will now be FILE.jpg waiting to upload
4. this will create a duplicate file if you uploaded file previously

### Expected behaviour

case of file extension should remain the same as stored on android device..JPG stays .JPG (uppercase) and not .jpg (lowercase)

### Actual behaviour

file extension is changed to lowercase. .JPG (uppercase) is being sent .jpg (lowercase).
files uploaded before as KIMG0001.JPG are now uploading and creating duplicates files named like KIMG0001.jpg.
this is duplicated on 10,000+ images and files ...

### Android version

12

### Device brand and model

kyocera

### Stock or custom OS?

Stock

### Nextcloud android app version

3.31.4

### Nextcloud server version

31.0.5

### Using a reverse proxy?

No

### Android logs

_No response_

### Server error logs

```bash

```

### Additional information

_No response_