Surveys and quizzes: replace the questions (only until the first response)

Body: { questions: [...] }, 1–50, in order; the whole list is replaced. Each: { type, prompt (≤300 chars), required?, options?, max?, answer?, id? }. type is single (pick one) or multi (pick any) with options (2–20 distinct texts), yesno, likert (disagree…agree), rating (max 5 or 10 stars), short or long (written). Quizzes: answer is the correct option index (single; yesno uses 1 = yes, 0 = no), a list of option indexes (multi), or a list of accepted texts (short); at least one question needs one. Send a question's id back to keep its picture. Refused with 409 once anyone has answered; the answer key can still be fixed with setAnswerKey.