fix nook subdomain routing

src/routes/checkout.tsx

@@ -0,0 +1,21 @@
+import { Switch, Match } from "solid-js";
+import { useSite } from "~/context/SiteContext";
+import NotFound from "./[...404]";
+import NookCheckout from "./nook/checkout";
+
+/**
+ * Host-aware checkout route — `/checkout`.
+ *
+ * Only The Nook has a checkout flow; all other sites fall back to 404.
+ * Mirrors the dispatch pattern in `src/routes/index.tsx`.
+ */
+export default function CheckoutPage() {
+  const site = useSite();
+  return (
+    <Switch fallback={<NotFound />}>
+      <Match when={site().id === "nook"}>
+        <NookCheckout />
+      </Match>
+    </Switch>
+  );
+}