DELETE /api/v1/chats/{id} called stop_item_tasks(id) before checking the
caller's chat.delete permission or ownership of the target chat. An
authenticated user who knew another user's chat id could therefore cancel that
chat's in-flight generation (streaming response, title or tag generation) even
though the deletion was then rejected. The chat id is discoverable through
legitimate read-only access to a shared chat or folder.
Reorder the handler to authorize first (admin, or owner holding chat.delete) and
only then cancel tasks and delete, matching the dedicated task-stop endpoint.
Legitimate deletions are unchanged; an unauthorized caller now returns 404 or 401
before any cancellation. The duplicated tag-cleanup and event-publish blocks are
merged.
Co-authored-by: GabrielGomesAL <193945687+GabrielGomesAL@users.noreply.github.com>
