Behavior: Triggers a full rebuild of all content definition override templates. This is typically used after system-level template changes or migrations to ensure all templates are up to date.

Authorization: Requires authentication and the user must be a system admin user (elevated privileges beyond regular admin).

Side Effects: Rebuilds all override templates in the system, which may temporarily affect content editing forms.

Error Scenarios: Returns 400 Bad Request if the user is not a system admin.