Publish or hide a questionnaire template as the Retraced admin

Flips the isActive flag on a Retraced-owned template. 1 publishes it into the shared pool, where it appears in every company's template picker; 0 withdraws it while leaving it listed and editable in the admin templates table. Only Retraced-owned templates are reachable — a company-owned template answers 404, whichever company the caller belongs to. Nothing else on the template is writable here: the name and content go through PUT /api/admin/questionnaires/templates/:id.