@keyframes btn-spin { to { transform: rotate(360deg); } }

.btn-spinner {
    display: inline-block;
    width: 14px; height: 14px;
    border: 2px solid rgba(255,255,255,0.35);
    border-top-color: #ffffff;
    border-radius: 50%;
    animation: btn-spin 0.75s linear infinite;
    flex-shrink: 0;
}

@media (prefers-reduced-motion: reduce) {
    .btn-spinner { animation: none; opacity: 0.7; }
}