Per directory sort settings

### ⚠️ This issue respects the following points: ⚠️

- [X] This is a **enhancement/feature request**. Not a [bug or question](https://github.com/gsantner/markor/issues/new/choose).
- [X] The topic is **not** already reported at [Issues](https://github.com/gsantner/markor/issues?q=#js-issues-search). _(I've searched it)_.
- [X] Markor **is** up to date. See [Releases](https://github.com/gsantner/markor/tags) for the latest version. Updates are available from [F-Droid](https://f-droid.org/en/packages/net.gsantner.markor/) and GitHub.
- [X] The wanted feature/enhancement is not present in the latest development version (git master). (Please [download](https://nightly.link/gsantner/markor/workflows/build-android-project/master) and try the test version of Markor, named **Marder**. Don't worry; Markor and Marder appear as completely separate applications. You can install both side-by-side, and Markor's settings are not touched. If your desired feature is present, you don't need to open this issue. The change will be part of the next Markor update.)

### Description

It would be good to have per-directory file sort settings

For example, I generally like to sort by name with folder first, but would like the Downloads folder to be sorted by time.

### Information

Android version:
Device:
App Version:

### Source

F-Droid

### Format / File type

Not specific

### Additional info / Log

_No response_

No files or tests are named in the issue. Start by locating Markor's file-browser sorting settings and inspect how the current sort choice is stored; the requested behavior is that different directories retain independent sort modes, such as name ordering for most folders and time ordering for Downloads.

Written by the indexing model from the issue text.