CVE-2026-50284: Craft CMS: Missing peer-permission check in `AssetsController::actionDeleteFolder` allows deletion of other users' assets

AssetsController::actionDeleteFolder() only requires the deleteAssets:<volume-uid> permission for the target folder. It never enforces deletePeerAssets:<volume-uid>, even though Assets::deleteFoldersByIds() cascades deletion to every descendant folder and every asset inside, regardless of who uploaded them. A low-privilege user who has been granted folder-management rights on a shared volume can therefore destroy assets uploaded by other users (peer assets), bypassing the per-asset peer-permission check that the sibling actionDeleteAsset endpoint correctly applies.

This is the same bug class that was just fixed in actionMoveFolder as GHSA-3w32-23wj-rxg3 (commit 05c2042, Apr 23 2026); the fix added requireVolumePermissionByFolder('deletePeerAssets', …) and savePeerAssets checks to the move endpoint but did not propagate to the delete-folder endpoint.