Add many cards and confirm in Markdown

Write. Add 1 to 100 prompt/answer pairs to one owned deck. An empty array is rejected. The bearer must own the deck. A missing deck or another token's deck is 404. Each card is eligible immediately. listDue still introduces at most that deck's newCardsPerDay today. The response includes deckId, count, and each cardId with its prompt and dueAt. answerIncluded is false. Answers are not returned. Inventory and listDue stay prompts only. The insert is all or nothing: if a later row fails, every card from this call is removed and the error is returned. Do not treat a non-201 as a partial add. After this write, re-run previewDeadlinePlan with this deckId. Choose newCardsPerDay with the person for this deck. There is no default of 20. When they have a deadline, call previewDeadlinePlan first: it returns ceil(remaining new cards / study days) as a floor. Weigh study time (more time, a higher number), that deadline floor, and card complexity (tiny facts such as times tables can be higher; a beefy card such as the five steps of a cycle must be lower). You may raise N above the floor or negotiate more study time. Send that integer. After bulk card adds, re-run previewDeadlinePlan with that deckId and consider applyDeadlinePlan or updateDeck. 0 introduces no new cards unless the caller asks for extras. Body is an object with deckId and cards. Same write as POST /dev/decks/{deckId}/cards/bulk.