Render a named zone

API-friendly zone rendering at POST /api/v6/zones/{event_name}. Intended for backend rendering where the caller supplies a bearer access token directly. Renders the zone identified by the event_name path parameter and returns the structured zone content as JSON. Pass zone input data in the request body. Returns an error when no content backs the zone. For browser or in-app rendering use POST /zones/{zone_name} instead.