Function run_server_until 

pub async fn run_server_until(
    routes: Router,
    shutdown: impl Future<Output = ()> + Send + 'static,
) -> Result<()>

Run the standard cja HTTP server until shutdown resolves, then stop accepting connections and finish in-flight requests. Preserves PORT, systemfd listeners, request tracing and cookie middleware.

The caller should bound the drain if a request can run indefinitely.