function ganti_logo_halaman_login() {
    // Menggunakan URL gambar langsung
    $logo_url = get_custom_logo() ? wp_get_attachment_image_url(get_theme_mod('custom_logo'), 'full') : 'URL_LENGKAP_KE_MEDIA_LOGO';
    ?>
        body.login div#login h1 a {
            background-image: url();
            background-size: contain;
            width: 100%;
            height: 80px; /* Sesuaikan tinggi logo */
        }
    <?php
}
add_action( 'login_enqueue_scripts', 'ganti_logo_halaman_login' );