Add page metadata across every route

The root layout exported no metadata, so routes without their own export
rendered no title at all, and no route had a description. Add a root
metadata block with a title template, Open Graph and Twitter defaults,
and fill in the routes that were missing tags.

- config/site.ts: description and env-driven absolute url for metadataBase
- home, /collections and /shop/collections: titles and descriptions
- products/[handle] and collections/[handle]: generateMetadata off the
  existing catalog fetchers, with canonical and OG image
- existing titles: drop the hand-written " — Shop" suffix now that the
  root template appends it

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_011x5jT4fJJCnqPx3umEvXRk

app/products/[handle]/page.tsx

@@ -1,5 +1,47 @@
+import type { Metadata } from 'next';
 import ProductDetail from '@/components/shopify/product-detail';
 import ProductRecommendations from '@/components/shopify/product-recommendations';
+import { getProduct } from '@/services/shopify/catalog';
+import { truncate } from '@/lib/utils';
+import { site } from '@/config/site';
+
+export async function generateMetadata({
+  params,
+}: {
+  params: Promise<{ handle: string }>;
+}): Promise<Metadata> {
+  const { handle } = await params;
+
+  // ProductDetail fetches client-side and renders its own empty state, so a
+  // failed lookup here falls back to generic tags rather than a 500.
+  const product = await getProduct(handle).catch(() => null);
+  if (!product) return { title: 'Product' };
+
+  const description = product.description
+    ? truncate(product.description, 160)
+    : site.description;
+  const image = product.images.edges[0]?.node;
+
+  return {
+    title: product.title,
+    description,
+    alternates: { canonical: `/products/${product.handle}` },
+    openGraph: {
+      title: product.title,
+      description,
+      url: `/products/${product.handle}`,
+      images: image
+        ? [{ url: image.url, alt: image.altText ?? product.title }]
+        : undefined,
+    },
+    twitter: {
+      card: 'summary_large_image',
+      title: product.title,
+      description,
+      images: image ? [image.url] : undefined,
+    },
+  };
+}
 
 export default function Page() {
   return (