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]/[genre]/page.tsx

@@ -6,6 +6,8 @@ import { PrismaClient } from '@prisma/client';
 import { notFound } from 'next/navigation';
 import { getLocalizedValue } from '@/lib/i18n';
 import { getTranslations } from 'next-intl/server';
+import { generateBaseMetadata } from '@/lib/metadata';
+import type { Metadata } from 'next';
 
 export const dynamic = 'force-dynamic';
 
@@ -15,6 +17,32 @@ interface PageProps {
     params: Promise<{ locale: string; genre: string }>;
 }
 
+export async function generateMetadata({ params }: PageProps): Promise<Metadata> {
+    const { locale, genre } = await params;
+    const decodedGenre = decodeURIComponent(genre);
+    
+    // Fetch genre to get localized name
+    const allGenres = await prisma.genre.findMany();
+    const currentGenre = allGenres.find(g => getLocalizedValue(g.name, locale) === decodedGenre);
+    
+    if (!currentGenre || !currentGenre.active) {
+        return await generateBaseMetadata(locale, genre);
+    }
+    
+    const genreName = getLocalizedValue(currentGenre.name, locale);
+    const genreSubtitle = getLocalizedValue(currentGenre.subtitle, locale);
+    
+    const title = locale === 'de'
+        ? `${genreName} - Hördle`
+        : `${genreName} - Hördle`;
+    
+    const description = genreSubtitle || (locale === 'de'
+        ? `Spiele Hördle im Genre ${genreName} und errate Songs aus kurzen Audio-Clips!`
+        : `Play Hördle in the ${genreName} genre and guess songs from short audio clips!`);
+    
+    return await generateBaseMetadata(locale, genre, title, description);
+}
+
 export default async function GenrePage({ params }: PageProps) {
     const { locale, genre } = await params;
     const decodedGenre = decodeURIComponent(genre);