Function mnemonic_iframe_handler 

pub async fn mnemonic_iframe_handler<E>(
    _state: State<UiState<DynGatewayApi<E>>>,
    _auth: UserAuth,
) -> impl IntoResponse
where
    E: Display + Send + Sync + 'static,

Handler for the initial iframe content (GET request). Returns a placeholder prompting the user to enter their password.