German "Umlaute" and colon seem to be unusable in file sync from server to app

### ⚠️ 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

Create a file named in a dir of your choice on the server:

`Rettungsgasse ist kein Straßenname: Die Abenteuer eines Notfallsanitäters und Feuerwehrmanns.m4a`

Try to sync with app -> error

### Expected behaviour

File syncs as expected

### Actual behaviour

Error syncing the file:
Invalid filename for local file

### Android version

14

### Device brand and model

Shift, Shiftphone 8.1

### Stock or custom OS?

Custom (explain in "additional information")

### Nextcloud android app version

3.35.1

### Nextcloud server version

30.0.15

### Using a reverse proxy?

Yes

### Android logs

_No response_

### Server error logs

```bash

```

### Additional information

ROM: /e/OS Vers: 2.9-a14-20250323478433-community-otter

No folder/ file under path in logfile explanation