Queue a translation of the quiz into one or more target languages.

• method=ai (default) — uses the platform LLM. Returns 202 Accepted
  with async=true. Poll status_url (or GET
  /quizzes/{quizId}/translation-status) for progress.
• method=crowdin — uploads the quiz to the project's Crowdin
  configuration (must be enabled via PUT /project/translation-connections).

If a translation is already running for this quiz the request is a no-op
and returns the in-progress status. Each completed language creates or
updates a sibling Quiz row (see GET /quizzes/{quizId}/translations).