fix layout and demo payment

web/app/cart/page.js

@@ -57,6 +57,11 @@ function PaymentForm({ clientSecret, totalAmount, onSuccess, onCancel }) {
       <p className="cart-payment-total">
         Total to pay: <strong>${parseFloat(totalAmount).toFixed(2)}</strong>
       </p>
+      <div className="cart-demo-banner">
+        <strong>Demo mode</strong> — no real charge. Use test card:
+        <span className="cart-demo-card">4242 4242 4242 4242</span>
+        · any future date · any 3-digit CVC
+      </div>
       <PaymentElement />
       {payError && <p className="cart-error-msg">{payError}</p>}
       <div className="cart-payment-actions">

web/app/globals.css

@@ -152,7 +152,7 @@ body {
 
 .image-links-container {
   display: grid;
-  grid-template-columns: repeat(4, 1fr);
+  grid-template-columns: repeat(3, 1fr);
   gap: 2rem;
   justify-content: center;
   align-items: stretch;
@@ -710,6 +710,7 @@ body {
   margin: 0 auto;
   padding: 0 2rem 4rem;
   display: grid;
+  grid-template-columns: repeat(3, 1fr);
   gap: 1.5rem;
 }
 
@@ -884,11 +885,15 @@ body {
   .slideshow-container {
     height: 300px;
   }
-  
+
   .image-links-container {
     grid-template-columns: repeat(2, 1fr);
     gap: 1.5rem;
   }
+
+  .info-content {
+    grid-template-columns: 1fr;
+  }
   
   .main-title {
     font-size: 2rem;
@@ -2637,6 +2642,25 @@ body {
   margin: 0;
 }
 
+.cart-demo-banner {
+  background: #fffbeb;
+  border: 1px solid #fcd34d;
+  border-radius: 8px;
+  padding: 0.6rem 0.9rem;
+  font-size: 0.85rem;
+  color: #78350f;
+  line-height: 1.5;
+}
+
+.cart-demo-card {
+  font-family: monospace;
+  font-weight: 700;
+  margin: 0 0.25rem;
+  background: #fef3c7;
+  padding: 0.1rem 0.35rem;
+  border-radius: 4px;
+}
+
 .cart-payment-actions {
   display: flex;
   flex-direction: column;