feat: search metadata, structured data and indexing rules

Only the production deployment may be indexed; testing and preview builds
answer with noindex and a closed robots file. The homepage now describes the
person, the services and the FAQ as structured data, and title, description
and the 404 page are written for what people search for.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

apps/web/app/(site)/sitemap.ts

@@ -1,14 +1,11 @@
 import type { MetadataRoute } from "next";
+import { SITE_URL } from "@/src/content/site";
 
-/** The site is a single page. */
+/**
+ * The site is a single page; the legal pages are not meant for search results.
+ * No modification date: it would have to be the date the content last changed,
+ * and a date that moves with every build teaches search engines to ignore it.
+ */
 export default function sitemap(): MetadataRoute.Sitemap {
-  const baseUrl = process.env.NEXT_PUBLIC_BASE_URL || "https://mintel.me";
-  return [
-    {
-      url: baseUrl,
-      lastModified: new Date(),
-      changeFrequency: "monthly",
-      priority: 1,
-    },
-  ];
+  return [{ url: `${SITE_URL}/` }];
 }