Save a questionnaire template as the Retraced admin

The save behind the Retraced-admin template builder. The admin twin of PUT /api/questionnaires/:id/builder — same write, same service — but gated on admin:questionnaire:write, which only RETRACED_ADMIN holds. sections and questions are the complete desired content, not a patch: rows present are created or updated, rows absent are deleted along with their answers and comments. name and description are always written; status is not settable here and keeps its stored value. A template stores no deadline of its own, so dueDate is always written as null — send it as null or omit it. The questionnaire must belong to the calling company — another company's is indistinguishable from a missing one and answers 404 — and a Retraced-owned questionnaire may only be saved by a Retraced admin, which this guard already guarantees. templates names the surface, not a filter: no is_template predicate is applied, so any questionnaire the caller company owns can be saved here. Once answer requests exist, an existing question's title, type, mandatory flag and options are frozen; adding a new question instead reopens every request so it can be answered. Answers the saved questionnaire in the same shape as the template builder read.