feat: remove contact form and switch canonical domain to mnqcatering.com

Drop the non-functional contact form (no backend wired up) and keep
the WhatsApp/phone contact path as the single call to action. Also
point site config, robots.txt, llms.txt, and every on-page domain
reference at www.mnqcatering.com ahead of the DNS cutover.

src/components/SiteFooter.astro

@@ -19,7 +19,7 @@ const whatsappAriaLabel = 'Contactar con MNQ por WhatsApp';
         <p>© 2025 MNQ Catering y Evento. Excelencia culinaria para los momentos más importantes de su vida.</p>
         <div style="display:flex;flex-direction:column;gap:0.35rem;margin-top:var(--space-4);">
           <a href="tel:+34678171513" class="footer-link" style="width:fit-content;">+34 678 17 15 13</a>
-          <a href="https://mnq.elkazurrotaberna.es" class="footer-link" style="width:fit-content;">mnq.elkazurrotaberna.es</a>
+          <a href="https://www.mnqcatering.com" class="footer-link" style="width:fit-content;">www.mnqcatering.com</a>
         </div>
       </div>