Give each route its own title and canonical, and add robots.txt plus a sitemap.

The root layout was stamping the homepage title and production root onto every page. Routes now supply a page segment through one em-dash template, canonicals follow the request path, and non-production hosts disallow crawlers.

Co-authored-by: Cursor <cursoragent@cursor.com>

app/sitemap.ts

@@ -0,0 +1,6 @@
+import type { MetadataRoute } from "next";
+import { buildPublicSitemap } from "../lib/publicSitemap";
+
+export default function sitemap(): MetadataRoute.Sitemap {
+  return buildPublicSitemap();
+}