Trashbin 'Deleted by' column shows 'Unknown' for Group Folder items deleted via desktop client

Description

When files are deleted from a Group Folder (via desktop client or web UI), the trashbin view at /apps/files/trashbin shows "Unknown" in the "Deleted by" column for all Group Folder items.

However, the oc_group_folders_trash table correctly stores the deleted_by value, and the backend TrashBackend.php correctly resolves it via $this->userManager->get($deletedBy).

Steps to reproduce

1. Enable Group Folders app and create a Group Folder shared with multiple users
2. User A deletes a file from the Group Folder via the Nextcloud desktop client
3. Admin views trashbin at /apps/files/trashbin
4. "Deleted by" column shows "Unknown" for the deleted file

Expected behavior

The "Deleted by" column should show the display name of the user who deleted the file (e.g., "ishizaka").

Actual behavior

The "Deleted by" column shows "Unknown" for all Group Folder trashbin items, even though the backend correctly stores and retrieves the deleted_by value.

Database evidence

SELECT * FROM oc_group_folders_trash;
-- trash_id | folder_id | name            | deleted_time | deleted_by
-- 1        | 1         | test.txt        | 1775308017   | ishizaka    ← correctly stored

Backend verification

• TrashManager.php correctly queries deleted_by from oc_group_folders_trash
• TrashBackend.php (line ~449) correctly resolves via $this->userManager->get($deletedBy)
• GroupTrashItem constructor correctly passes ?IUser $deletedBy to parent TrashItem
• TrashbinPlugin.php correctly exposes TRASHBIN_DELETED_BY_ID and TRASHBIN_DELETED_BY_DISPLAY_NAME via WebDAV PROPFIND

The issue appears to be in the frontend rendering — the WebDAV properties are likely not being picked up by the trashbin JavaScript frontend.

Environment

• Nextcloud: 33.0.1
• Group Folders: latest from app store
• Primary storage: S3-compatible objectstore (Cloudflare R2)
• PHP: 8.3.6
• OS: Ubuntu 24.04 LTS
• Desktop client: 33.0.2 (Windows)

Start at the trashbin view at /apps/files/trashbin and trace how the frontend consumes the WebDAV properties exposed by TrashbinPlugin.php. Compare those properties with the data passed through TrashManager.php, TrashBackend.php, and GroupTrashItem; done means Group Folder entries display the deleting user's name instead of "Unknown".