Add Snipcart product validation endpoint and improve product gallery

- Add route handler for /validate.json to enable Snipcart product validation
- Update product gallery to display all product images instead of just the first one
- Fix CSS styling for product gallery list items
- Update home page to use first sorted image as product cover

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

assets/css/style.css

@@ -1106,10 +1106,13 @@ body.is-fullscreen {
   content: "← ";
 }
 
-.section__product figure {
+.section__product .product-gallery li {
+  list-style: none;
+}
+.section__product .product-gallery figure {
   aspect-ratio: 1/1;
 }
-.section__product figure img {
+.section__product .product-gallery figure img {
   width: 100%;
   height: 100%;
   -o-object-fit: contain;

assets/css/template/shop/_section--product.scss

@@ -22,13 +22,18 @@
 }
 
 .section__product {
-  figure {
-    aspect-ratio: 1/1;
+  .product-gallery {
+    li {
+      list-style: none;
+    }
+    figure {
+      aspect-ratio: 1/1;
 
-    img {
-      width: 100%;
-      height: 100%;
-      object-fit: contain;
+      img {
+        width: 100%;
+        height: 100%;
+        object-fit: contain;
+      }
     }
   }