Enhance product detail page and header with API-driven navigation.

Add gallery lightbox, tabs, marketplace CTAs, and similar products on product pages; load the business logo and level-2 category dropdown in the header.

Co-authored-by: Cursor <cursoragent@cursor.com>

src/lib/user-product-gallery.ts

@@ -0,0 +1,9 @@
+export function resolveProductGallery(product: {
+  images?: { url: string }[] | null;
+  imageUrl?: string | null;
+}) {
+  const fromImages =
+    product.images?.map((img) => img.url).filter(Boolean) ?? [];
+  if (fromImages.length > 0) return fromImages;
+  return product.imageUrl ? [product.imageUrl] : [];
+}