Trashbin move can OOM due to full folder size recalculation

[hweihwang]

Description

WebDAV DELETE can hit PHP memory limit during trashbin move, leaving request aborted. The memory spike appears tied to folder size recalculation in cache updates during Trashbin::move2trash().

This surfaces in Ticket#9687404: deleting a tiny file via WebDAV consumed >500MB and the request died. The trash payload exists, but metadata/cache may be inconsistent. Related to #56493, but the root cause here is the memory‑OOM path, not just non‑atomic metadata ordering.

Steps to reproduce (likely)

1. Use a user with a very large folder (many children) in home storage.
2. Delete a file from that folder via WebDAV/UI (trashbin enabled).
3. Observe PHP memory growth during Trashbin::move2trash().

Actual result

• WebDAV DELETE hits memory limit (PHP fatal), request aborts.
• Inconsistent trash state possible: payload moved but DB/cache incomplete.

Expected result

• Trash move should not require full folder scan or excessive memory.
• Delete should be robust even on large folders.

Analysis / suspected root cause

During trash move, cache updater calls renameFromStorage() which triggers Cache::correctFolderSize() for source and target. That calls calculateFolderSizeInner() and fetchAll() on child entries (large folders) which can blow memory.

Relevant paths:

• apps/files_trashbin/lib/Trashbin.php → move2trash() → Updater::renameFromStorage() / update()
• lib/private/Files/Cache/Updater.php → copyOrRenameFromStorage() → Cache::correctFolderSize()
• lib/private/Files/Cache/Cache.php → calculateFolderSizeInner() (fetchAll())

Proposed direction

• Add a fast path for trash moves to avoid full folder size recalculation; use known size delta to update parent sizes, or defer size correction to background.
• Alternatively: add optional size‑delta parameter to renameFromStorage() and skip correctFolderSize() when provided.

Notes

PR #57360 mitigates orphaned metadata by inserting files_trash row before payload move, but does not fix memory‑OOM path.