Feature request: Backup and restore of bucket configurations

### Please agree to the following

- [x] I have searched [existing issues](https://github.com/cryptomator/android/issues?q=) for duplicates
- [x] I agree to follow this project's [Code of Conduct](https://github.com/cryptomator/android/blob/develop/.github/CODE_OF_CONDUCT.md)

### Summary

Allow users to export and import (config file and qrcode) bucket configuration settings (without encryption password)

### Motivation

It would be really useful to have the ability to backup and restore the configuration of buckets in Cryptomator for Android.

Of course, this wouldn’t include the encryption password — just the connection details and preferences, such as:

Bucket name

Login / password (for the bucket itself)

URI / endpoint

Configuration settings

Personally, I’m using an S3-compatible bucket, but the idea would be that users could easily export and import their bucket configuration when changing devices or reinstalling the app.

Even better, the ability to restore configurations via a QR code would make the process extremely convenient! 🚀

Thanks for considering this — it would make setup and migration much smoother for many users.

### Considered Alternatives

_No response_

### Anything else?

_No response_