Adds a translation of a question in one language and republishes the survey's call routing. Validation requires language, a nonblank question_text and a question_actions array in which every action has a nonblank app, while the actions actually stored come from custom_actions — send both. A language the question is already translated into is rejected with 409. No audio is generated here, and access is decided by the survey the question actually belongs to rather than the survey ID in the path.