chore: add nextjs template

frontend-nextjs/components/Footer.tsx

@@ -0,0 +1,7 @@
+export default function Footer() {
+  return (
+    <footer style={{ padding: "24px", textAlign: "center", color: "#666" }}>
+      <small>Sample footer for Next.js clone</small>
+    </footer>
+  );
+}

frontend-nextjs/components/Header.tsx

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+export default function Header() {
+  return (
+    <header style={{ padding: "20px 24px", background: "#ffffff", borderBottom: "1px solid #e2e2e2" }}>
+      <div style={{ maxWidth: 1100, margin: "0 auto", display: "flex", alignItems: "center", gap: 16 }}>
+        <div style={{ fontWeight: 700 }}>Brand</div>
+        <nav style={{ display: "flex", gap: 12, fontSize: 14 }}>
+          <a href="/" style={{ textDecoration: "none", color: "inherit" }}>Home</a>
+          <a href="/search" style={{ textDecoration: "none", color: "inherit" }}>Search</a>
+        </nav>
+      </div>
+    </header>
+  );
+}

frontend-nextjs/components/ProductCard.tsx

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+import { Product } from "@/lib/api";
+
+export default function ProductCard({ product }: { product: Product }) {
+  return (
+    <article
+      style={{
+        border: "1px solid #e1e1e1",
+        background: "#fff",
+        borderRadius: 12,
+        padding: 12,
+        display: "grid",
+        gap: 8
+      }}
+    >
+      <div
+        style={{
+          height: 160,
+          borderRadius: 8,
+          background: `url(${product.image_url}) center/cover no-repeat`
+        }}
+      />
+      <h3 style={{ margin: 0, fontSize: 14 }}>{product.title}</h3>
+      <div style={{ fontWeight: 600 }}>${(product.price_cents / 100).toFixed(2)}</div>
+      <a href={`/listing/${product.id}/${encodeURIComponent(product.title)}`}>View</a>
+    </article>
+  );
+}