New items from other devices do not appear

## Summary

When a file is uploaded to the Nextcloud server from another device (confirmed visible in the web interface), it does not appear as a Virtual File placeholder on a second macOS device. The Desktop client reports "Everything is synced" with no errors. The only working fix is to disable and re-enable Virtual Files entirely, which forces a full re-enumeration from the server.

## Environment

- **Nextcloud Desktop Client:** 3.3.0.5
- **macOS:** 15.7.6 (Sequoia)
- **Hardware:** MacBook Air M2 (Apple Silicon)
- **Virtual Files mode:** Enabled (macOS File Provider Extension)
- **Nextcloud Server:** self-hosted

## Steps to Reproduce

1. Device A (old Mac, classic sync): Copy a new file into the Nextcloud sync folder
2. Wait for the file to upload — confirm it is visible in the Nextcloud web interface
3. On Device B (MacBook Air, Virtual Files enabled): Open the same folder in Finder or Terminal
4. The file does **not** appear as a Virtual File placeholder

## Expected Behavior

The new file should appear as a placeholder (Virtual File) on Device B within a reasonable time after the upload to the server is complete.

## Actual Behavior

- The file is missing. Running `ls` in Terminal on the affected folder returns results without the new file.
- The Desktop client shows no errors and reports "Everything is synced."
- No activity for the specific file is shown in the client's activity log.
- The file is clearly present on the server (visible in web interface).

## Workaround

Disabling Virtual Files in the Desktop client and immediately re-enabling it triggers a complete re-enumeration from the server, after which the file appears correctly.

This workaround is disruptive: all local placeholders are removed and must be re-fetched, which takes considerable time depending on the number of files.

## What Does NOT Help

- Restarting the Nextcloud Desktop client
- Running `killall -9 fileproviderd` (the daemon restarts but continues to return stale/incomplete listings)
- Waiting — the file never appears on its own without the disable/re-enable cycle

## Additional Context

This appears to be a recurring issue with the macOS File Provider integration. Related reports:
- #7979 — Virtual Files fail to sync / appear on macOS
- #8599 — Finder shows "Nextcloud is signed out" while client reports OK
- https://help.nextcloud.com/t/macos-virtual-files-not-being-synced/231796
- https://help.nextcloud.com/t/ongoing-problems-with-macos-virtual-file-sync/232910

The root cause seems to be that `fileproviderd` caches the folder enumeration and does not reliably poll the server for changes, while the Desktop client considers its own upload queue empty and reports "synced" — creating a false sense of consistency. A targeted re-enumeration of specific remote folders (without requiring a full Virtual Files reset) would solve this.