feat: update Impressum with correct company data + fix email domain

- Impressum: MC Cars GmbH, Gaisfeld 1/2, 8564 Krottendorf-Gaisfeld
- FN 675751 b, Landesgericht für Zivilrechtssachen Graz
- Geschäftsführer: Christian Leski, Marco Schober
- UID placeholder (wird nachgereicht)
- Email domain: mccars.at → mc-cars.at across all pages
- Social links: mccars → mc-cars

frontend/index.html

@@ -65,8 +65,8 @@
         "priceRange": "€€€",
         "serviceType": "Ferrari-Vermietung",
         "sameAs": [
-            "https://www.facebook.com/mccars",
-            "https://www.instagram.com/mccars"
+            "https://www.facebook.com/mc-cars",
+            "https://www.instagram.com/mc-cars"
         ]
     }
     </script>
@@ -387,7 +387,7 @@
 
                 <div>
                     <h4 data-i18n="footerContact">Kontakt</h4>
-                    <a href="mailto:hello@mccars.at">hello@mccars.at</a>
+                    <a href="mailto:hello@mc-cars.at">hello@mc-cars.at</a>
                     <a href="tel:+43316880000">+43 316 880000</a>
                 </div>
             </div>