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]/layout.tsx

@@ -8,6 +8,7 @@ import { notFound } from 'next/navigation';
 import { headers } from 'next/headers';
 
 import { config } from "@/lib/config";
+import { generateBaseMetadata } from "@/lib/metadata";
 import InstallPrompt from "@/components/InstallPrompt";
 import AppFooter from "@/components/AppFooter";
 
@@ -21,10 +22,10 @@ const geistMono = Geist_Mono({
     subsets: ["latin"],
 });
 
-export const metadata: Metadata = {
-    title: config.appName,
-    description: config.appDescription,
-};
+export async function generateMetadata({ params }: { params: Promise<{ locale: string }> }): Promise<Metadata> {
+    const { locale } = await params;
+    return await generateBaseMetadata(locale);
+}
 
 export const viewport: Viewport = {
     themeColor: config.colors.themeColor,