feat: Add comprehensive SEO implementation

- Add robots.txt with admin/API blocking
- Add dynamic sitemap.xml with static pages and genre pages
- Implement full meta tags (Open Graph, Twitter Cards, Canonical, Alternates)
- Add SEO helper functions for domain detection and URL generation
- Add generateMetadata to all pages (homepage, about, genre, special)
- Support automatic domain detection for hoerdle.de and hördle.de
- Add SEO configuration to lib/config.ts

app/[locale]/about/page.tsx

@@ -1,10 +1,22 @@
 import { getTranslations } from "next-intl/server";
 import { Link } from "@/lib/navigation";
+import { generateBaseMetadata } from "@/lib/metadata";
+import type { Metadata } from "next";
 
 interface AboutPageProps {
   params: Promise<{ locale: string }>;
 }
 
+export async function generateMetadata({ params }: AboutPageProps): Promise<Metadata> {
+  const { locale } = await params;
+  const t = await getTranslations({ locale, namespace: "About" });
+  
+  const title = t("title");
+  const description = t("intro");
+  
+  return await generateBaseMetadata(locale, "about", title, description);
+}
+
 export default async function AboutPage({ params }: AboutPageProps) {
   const { locale } = await params;
   const t = await getTranslations({ locale, namespace: "About" });