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]/special/[name]/page.tsx

@@ -5,6 +5,8 @@ import { Link } from '@/lib/navigation';
 import { PrismaClient } from '@prisma/client';
 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';
 
@@ -14,6 +16,30 @@ interface PageProps {
     params: Promise<{ locale: string; name: string }>;
 }
 
+export async function generateMetadata({ params }: PageProps): Promise<Metadata> {
+    const { locale, name } = await params;
+    const decodedName = decodeURIComponent(name);
+    
+    // Fetch special to get localized name
+    const allSpecials = await prisma.special.findMany();
+    const currentSpecial = allSpecials.find(s => getLocalizedValue(s.name, locale) === decodedName);
+    
+    if (!currentSpecial) {
+        return await generateBaseMetadata(locale, `special/${name}`);
+    }
+    
+    const specialName = getLocalizedValue(currentSpecial.name, locale);
+    const specialSubtitle = getLocalizedValue(currentSpecial.subtitle, locale);
+    
+    const title = `★ ${specialName} - Hördle`;
+    
+    const description = specialSubtitle || (locale === 'de'
+        ? `Spiele das Hördle-Special "${specialName}" und errate Songs aus kurzen Audio-Clips!`
+        : `Play the Hördle special "${specialName}" and guess songs from short audio clips!`);
+    
+    return await generateBaseMetadata(locale, `special/${name}`, title, description);
+}
+
 export default async function SpecialPage({ params }: PageProps) {
     const { locale, name } = await params;
     const decodedName = decodeURIComponent(name);