feat: Implement default payment method for pickup and enhance payment method handling in CartTab and PaymentMethodSelector components

src/components/profile/CartTab.js

@@ -223,6 +223,15 @@ class CartTab extends Component {
   handleDeliveryMethodChange = (event) => {
     const newDeliveryMethod = this.normalizeDeliveryMethod(event.target.value);
     const deliveryCost = this.orderService.getDeliveryCost();
+
+    // Pickup should default to in-store payment.
+    if (newDeliveryMethod === "Abholung") {
+      this.setState({
+        deliveryMethod: newDeliveryMethod,
+        paymentMethod: "cash",
+      });
+      return;
+    }
     
     // Get optimal payment method for the new delivery method
     const optimalPaymentMethod = CheckoutValidation.getOptimalPaymentMethod(