Delete quizzes

Delete up to BATCH_MAX_ITEMS quizzes in a single request (CASCADE soft-delete).

Each item is a resource-identifier object ({type, id}). Per item the quiz is resolved org-scoped + live (already-deleted / wrong-org / malformed ids surface as per-item not_found) and, in that item's own atomic block, the quiz's OWN questions and their answers are SOFT-deleted, its question-bank ASSIGNMENTS are HARD-removed, and finally the quiz itself is SOFT-deleted. The shared question banks (and their bank-owned questions / answers) are left untouched — a quiz only owns questions where question.quiz == quiz.

Within-batch duplicate detection is first-wins on id; each deleted item echoes the caller's input id. Response is 200 if all deleted, 207 if any failed, 400 if the envelope is empty or over the cap. See api_v2/docs/batch-responses.md for the envelope shape.

Required OAuth scope: quizzes:write