[Feature Request] [i18n] Support Android's per-app language setting

### Before you submit

- [x] I have searched the issue tracker for [open](https://github.com/Droid-ify/client/issues) and [closed](https://github.com/Droid-ify/client/issues?q=is%3Aissue+is%3Aclosed) issues that are similar to the feature request I want to file, without success.
- [x] I'm not requesting app support for a specific repo — that's up to repo maintainers
- [x] I understand this might not get built (Droid-ify is maintained by a single person)

### What's the problem?

The language selector in the app is kind of a legacy UI - now that Android supports per-app language settings (`System Settings` → `System` → `Languages` → `App languages`), we should support that and eventually get rid of the in-app language selector.

### What would help?

https://support.google.com/android/answer/12395118
https://developer.android.com/guide/topics/resources/app-languages
https://android-developers.googleblog.com/2022/11/per-app-language-preferences-part-1.html

### Alternatives?

_No response_

### Anything else?

Click to see screenshot

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