Fix shop/related/wishlist grids not equalizing card heights

ProductCard already has a h-full + flex-1 spacer specifically to keep
every card in a row the same height regardless of content (title wrap,
subline wrap, low-stock line) — but all three grids using it set
items-start on the grid container, which overrides the default stretch
and silently defeats that. A product whose subline wraps to 2 lines made
its card taller than its row siblings instead of them matching. Dropping
items-start (default items-stretch) fixes all three call sites.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01J1Hu5bZ1kZUgKhab6yNwCt

app/cart/components/RelatedProducts.tsx

@@ -129,7 +129,9 @@ export function RelatedProducts({
           (opacity: 0) — invisible. Not worth chasing a fix for a
           scroll-reveal nicety on a list that mutates; a static grid
           renders correctly with no animation risk. */}
-      <div className="grid items-start grid-cols-1 sm:grid-cols-12 gap-6 sm:gap-[var(--layout-grid-gap)] w-full max-w-[75rem]">
+      {/* No items-start — see ProductGrid.tsx's own comment on why that
+          silently defeats ProductCard's h-full equal-height design. */}
+      <div className="grid grid-cols-1 sm:grid-cols-12 gap-6 sm:gap-[var(--layout-grid-gap)] w-full max-w-[75rem]">
         {displayProducts.map((product, i) => (
           <ProductCard
             key={product.id}