Add shop, cart, versand pages and Impulse & Tipps detail page

- New /shop overview, /cart (real cart state via useSyncExternalStore),
  /versand (shipping policy page with TOC) and /newsletter detail page
- Cart: quantity/removal, order summary, related-products cross-sell
  with randomized picks, VersandModal quick-reference instead of
  navigating away, MwSt. disclosure next to unit prices
- Add-to-cart UX: inline success feedback (green state) plus a
  fly-to-navbar-cart-icon animation (CartFlyProvider) with a delayed
  badge count-up; AddToCartButton no longer navigates straight to /cart
- Shared lib/products.ts catalog and lib/shipping.ts constants (cost,
  free-shipping threshold, handling/transit days) so cart, trust badges
  and the versand page can never drift apart
- Fix Navbar smooth-scroll easing (ease-out instead of ease-in-out, no
  more perceived start delay); compress newsletter modal photo
  2.4MB -> 85KB to fix first-open jank

app/cart/page.tsx

@@ -0,0 +1,30 @@
+import type { Metadata } from "next";
+import { CartContent } from "./components/CartContent";
+import { RelatedProducts } from "./components/RelatedProducts";
+import { TrustRow } from "../components/TrustRow";
+import { Footer } from "../components/Footer";
+
+// robots: noindex — transactional page (mirrors a specific shopper's cart
+// contents), per the figma-to-nextjs skill's Step 5 guidance: indexing
+// this wastes crawl budget and could surface cart state in search results.
+export const metadata: Metadata = {
+  title: "Warenkorb",
+  description: "Dein Warenkorb bei einfach produktiv.",
+  robots: {
+    index: false,
+    follow: true,
+  },
+};
+
+export default function CartPage() {
+  return (
+    <>
+      <main className="flex flex-col flex-1 bg-bg-base">
+        <CartContent />
+        <RelatedProducts />
+        <TrustRow />
+      </main>
+      <Footer />
+    </>
+  );
+}