Local folder picker crashes the app: UncheckedIOException from Files.list() escapes the IOException catch in FileHelper.listDirectoryEntries

### ⚠️ Before posting ⚠️

- [x] This is a **bug**, not a question or an enhancement.
- [x] I've [searched for similar issues](https://github.com/nextcloud/android/issues) and didn't find a duplicate.
- [x] I've written a clear and descriptive title for this issue, not just "Bug" or "Crash".
- [x] I agree to follow Nextcloud's [Code of Conduct](https://nextcloud.com/contribute/code-of-conduct/).

### Steps to reproduce

1. Settings → Auto upload → ⋮ → "Set custom folder".
2. In the local folder picker, browse into a large directory under `/storage/emulated/0/Android/media/…` (in my case `com.whatsapp/WhatsApp/Media/WhatsApp Images`, ~11 600 files, and its `Sent` subdirectory).
3. Keep the device busy at the same time (several auto-upload rules were uploading in the background here).

The directory read fails part-way through iteration with `Software caused connection abort` from the emulated-storage layer. That failure is intermittent and I cannot trigger it on demand — but when it happens, the app dies instead of showing an empty/partial list.

### Expected behaviour

A failed directory read is logged and the picker shows what it could read (the `catch` in `FileHelper.listDirectoryEntries` is clearly written with exactly that intent).

### Actual behaviour

The whole app is killed. The exception escapes the background executor task, so there is no chance to recover.

The `catch` cannot fire, and this is visible in the source rather than inferred:

`FileHelper.listDirectoryEntries` (34.1.1) uses `Files.list(...)`, whose lazy stream reports directory-read failures from the terminal operation as **`java.io.UncheckedIOException`** — a `RuntimeException`, not an `IOException`:

```kotlin
return try {
Files.list(directory.toPath())
.map { it.toFile() }
…
.collect(Collectors.toList())
} catch (e: IOException) { // never reached for UncheckedIOException
Log_OC.d(TAG, "listDirectoryEntries: $e")
emptyList()
}
```

`LocalFileListAdapter.loadRemainingEntries()` calls it on a pool thread with no guard, so the `UncheckedIOException` terminates the thread and takes the process with it.

Two small notes that may save reviewer time:

* Adding `catch (e: UncheckedIOException)` (or catching its `cause`) next to the existing `IOException` branch restores the intended behaviour.
* `FileHelper` on master has since been rewritten to `forEachDirectoryPage` using `Files.newDirectoryStream` with `catch (IOException)` + `catch (DirectoryIteratorException)`, which does cover the iteration failure. So master may already be fine and this report is mainly about the released 34.1.1 line — worth confirming whether a backport is wanted.

### Android version

17

### Device brand and model

Samsung SM-F976B (Galaxy Z Fold8), stock

### Stock or custom OS?

Stock

### Nextcloud android app version

34.1.1 (340010190, gplay)

### Nextcloud server version

31.0.14

### Using a reverse proxy?

Yes

### Android logs

### Cause of error
```java
Exception in thread "pool-27-thread-1" java.io.UncheckedIOException: java.nio.file.FileSystemException: /storage/emulated/0/Android/media/com.whatsapp/WhatsApp/Media/WhatsApp Images/Sent: Software caused connection abort
at java.nio.file.Files$2.hasNext(Files.java:3729)
at java.util.Spliterators$IteratorSpliterator.tryAdvance(Spliterators.java:1949)
at java.util.stream.ReferencePipeline.forEachWithCancel(ReferencePipeline.java:156)
at java.util.stream.AbstractPipeline.copyIntoWithCancel(AbstractPipeline.java:592)
at java.util.stream.AbstractPipeline.copyInto(AbstractPipeline.java:578)
at java.util.stream.AbstractPipeline.wrapAndCopyInto(AbstractPipeline.java:564)
at java.util.stream.ReduceOps$ReduceOp.evaluateSequential(ReduceOps.java:921)
at java.util.stream.AbstractPipeline.evaluate(AbstractPipeline.java:267)
at java.util.stream.ReferencePipeline.collect(ReferencePipeline.java:748)
at com.nextcloud.utils.FileHelper.listDirectoryEntries(FileHelper.kt:31)
at com.owncloud.android.ui.adapter.LocalFileListAdapter.loadRemainingEntries(LocalFileListAdapter.java:434)
at com.owncloud.android.ui.adapter.LocalFileListAdapter.lambda$swapDirectory$2(LocalFileListAdapter.java:405)
at com.owncloud.android.ui.adapter.LocalFileListAdapter.$r8$lambda$EFQ1jO9hT3yhM5CFqUk4qO5Vyvg(LocalFileListAdapter.java:0)
at com.owncloud.android.ui.adapter.LocalFileListAdapter$$ExternalSyntheticLambda0.run(D8$$SyntheticClass:0)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1100)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
at java.lang.Thread.run(Thread.java:1572)
Caused by: java.nio.file.FileSystemException: /storage/emulated/0/Android/media/com.whatsapp/WhatsApp/Media/WhatsApp Images/Sent: Software caused connection abort
at sun.nio.fs.UnixDirectoryStream$UnixDirectoryIterator.readNextEntry(UnixDirectoryStream.java:180)
at sun.nio.fs.UnixDirectoryStream$UnixDirectoryIterator.hasNext(UnixDirectoryStream.java:210)
at java.nio.file.Files$2.hasNext(Files.java:3727)
…
```

### App information
* ID: `com.nextcloud.client`
* Version: `340010190`
* Build flavor: `gplay`

### Device information
* Brand: `samsung`
* Device: `q8q`
* Model: `SM-F976B`
* Id: `CP2A.260605.016`
* Product: `q8qxeea`

### Firmware
* SDK: `37`
* Release: `17`
* Incremental: `F976BXXS2AZH7`

Start in FileHelper.kt at listDirectoryEntries and inspect how Files.list() reports failures during terminal iteration; then check LocalFileListAdapter.kt at loadRemainingEntries() for the background-task boundary. Confirm that directory-read failures no longer terminate the app, that the picker retains the readable entries or shows an empty list, and whether the fix needs backporting to the 34.1.1 line.

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