handleQuantityButton(button) { const container = button.parentElement; const input = container?.querySelector('input[data-qty-input]'); const display = container?.querySelector('[data-qty-render]');
if (!input) return;
const currentQty = parseInt(input.value) || 0; const isPlus = button.dataset.qty === 'plus'; const newQty = isPlus ? currentQty + 1 : Math.max(0, currentQty - 1);