Auto focus search text box

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

- [x] This is a **bug**. Not a [question or feature request](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 bug is still 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 settings are not touched. In case the issue is resolved there, you don't need to create a bug report. The change will be part of the next Markor update.)

### Description

When using the search menu in the file explorer for the first time since app start, it does not automatically focus the query text box and opens the keyboard. I am very lazy and I would like Markor to do just that. The app does auto focus, but only after completing the first search and then re-opening the search menu. See the steps below.

### Steps to reproduce

1. Close the app completely (also from background)
2. Start the app
3. Open the search menu in the file explorer
4. It does not auto focus the text box
5. Enter some search query, and press "OK"
6. Close the appearing search results dialog
7. You're back in the file explorer
8. Open the search menu again
9. It automatically focuses the query text box, selects all text and opens the keyboard

### Information

Android version: 16
Device: Samsung Galaxy A56 5G
App Version: 2.16.1

### Source

F-Droid

### Format / File type

Not specific

### Additional info / Log

```shell
-
```

Start by reproducing the first-use search flow in the file explorer after a cold app launch, then compare it with reopening search after a completed query. Trace the file explorer's search-menu entry point and its query text box behavior. Done means the first opening focuses the box, selects text, and opens the keyboard consistently.

Written by the indexing model from the issue text.