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)/not-found.tsx

@@ -1,9 +1,8 @@
 export const metadata = {
-  title: "404 - Seite nicht gefunden | Marc Mintel",
-  description: "Diese Seite konnte leider nicht gefunden werden.",
+  title: "Page not found",
+  description: "This page does not exist.",
 };
 
-import Link from "next/link";
 import { Button } from "@/src/components/Button";
 
 export default function NotFound() {
@@ -14,19 +13,15 @@ export default function NotFound() {
           Error 404
         </span>
         <h1 className="text-5xl md:text-7xl font-black text-slate-900 tracking-tighter">
-          System-Anomalie.
+          Page not found.
         </h1>
         <p className="text-xl md:text-2xl text-slate-500 font-serif italic max-w-xl mx-auto leading-relaxed">
-          Die angeforderte URL existiert nicht in dieser Zeitleiste.
-          Möglicherweise wurde die Seite verschoben oder gelöscht.
+          This address does not exist. The page may have been moved or removed.
         </p>
 
         <div className="pt-8 flex flex-col sm:flex-row items-center justify-center gap-4">
           <Button href="/" variant="primary">
-            Zurück zur Basis
-          </Button>
-          <Button href="/blog" variant="outline">
-            Aktuelle Artikel lesen
+            Back to the homepage
           </Button>
         </div>