Locked out of app due to upload queue

### Steps to reproduce
1. Add a new auto-upload folder with lots (10000 files+) of existing content (in my case, Android/media/com.whatsapp), with a majority of the content already present on the server
2. Enable 'also upload existing content'
3. Save & active the auto-upload rule
4. Close app, wait for uploading to start (5 minutes)
5. Try to open app, frozen on launch screen (blue screen with nextcloud logo)

### Expected behaviour
- I should be able to open the app, edit upload settings.

### Actual behaviour
- App freezes on start, constant `Nextcloud isn't responding: Wait/Close app` system dialog popups, even when not using the app.

### Can you reproduce this problem on https://try.nextcloud.com?
Haven't tried, would have to set up a new phone with 10000 test files. Could do this on request though.

### Environment data
Android version: Android 11

Device model: Fairphone 3+

Stock or customized system: LOS microG version

Nextcloud app version: 3.18.1

Nextcloud server version: 22.3

Reverse proxy: NGINX

### Notes
Possibly relevant: A significant amount of the content that would be uploaded is already present on my server, causing file upload conflicts. This would only be an issue on initial sync, afterwards all new content shouldn't conflict (and I would want to know about any conflicts)