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.

astro.config.mjs

@@ -3,7 +3,7 @@ import node from '@astrojs/node';
 import sitemap from '@astrojs/sitemap';
 
 export default defineConfig({
-  site: 'https://mnq.elkazurrotaberna.es',
+  site: 'https://www.mnqcatering.com',
   output: 'server',
   adapter: node({
     mode: 'standalone',