Adds a question to a survey, generates its spoken audio and republishes the survey's call routing. question_number defaults to one past the highest number in use, and a number already taken is rejected. When actions is supplied it must include the survey's default language, and each language entry must carry exactly one of question_text or custom_actions. Entries are written for the default language and every language already used elsewhere in the survey, filling gaps with the default language's text or a Question N placeholder — a language that appears only in this request is not added to that set.