Calendar backup used wrong username

### ⚠️ 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. Open the Nextcloud app
2. Settings --> Contacts & Calendar backup
3. Set Calendar slider ON
4. Tap "Back up now"
5. Go to "All files" --> ". Calendar-Backup"
6. Locate and inspect the "ics" file created.

### Expected behaviour

Expected to see an ics file with MY name associated with it, and with MY calendar entries.

### Actual behaviour

The ics file here used the name of my wife's calendar account, not mine. We both have Android phones with Google accounts, and we share calendar entries. Inspecting the ics file, it appears to only have her calendar entries -- NONE of mine.
At minimum, save MY calendar entries, and name the ics file appropriately using MY name.
Optionally, if it sees multiple users in the calendar, it could prompt and ask if I also want to backup those entries.

### Android version

13

### Device brand and model

Samsung S20FE

### Stock or custom OS?

Stock

### Nextcloud android app version

3.24.0 RC2

### Nextcloud server version

Hub 3 (25.0.3)

### Using a reverse proxy?

No

### Android logs

_No response_

### Server error logs

_No response_

### Additional information

Could not locate nextcloud.log on my phone's internal storage, even with hidden files visible.
I am not a beta nor dev user.