feat(web): add SEO optimization — JSON-LD, dynamic sitemap, meta tags for listings

Add comprehensive SEO support for property listing pages to improve
organic search visibility and social sharing.

Changes:
- Convert listing detail page from client-only to server component wrapper
  with generateMetadata() for per-listing title, description, OG tags,
  canonical URLs, and hreflang alternates
- Add JSON-LD structured data (Schema.org RealEstateListing) with price,
  location, property specs, and breadcrumb markup
- Add Website JSON-LD with SearchAction to root layout
- Upgrade sitemap.xml to dynamically include all active listings across
  both locales (vi, en) with ISR revalidation
- Improve robots.txt with pagination/sort exclusions and GPTBot block
- Create server-side fetch utility (listings-server.ts) for SSR data
- Extract client UI into ListingDetailClient component

Co-Authored-By: Paperclip <noreply@paperclip.ing>

apps/web/app/robots.ts

@@ -1,16 +1,28 @@
 import type { MetadataRoute } from 'next';
 
-export default function robots(): MetadataRoute.Robots {
-  const siteUrl = process.env['NEXT_PUBLIC_SITE_URL'] || 'https://goodgo.vn';
+const siteUrl = process.env['NEXT_PUBLIC_SITE_URL'] || 'https://goodgo.vn';
 
+export default function robots(): MetadataRoute.Robots {
   return {
     rules: [
       {
         userAgent: '*',
         allow: '/',
-        disallow: ['/dashboard/', '/admin/', '/auth/', '/api/'],
+        disallow: [
+          '/dashboard/',
+          '/admin/',
+          '/auth/',
+          '/api/',
+          '/*?sort=',      // avoid indexing duplicate sort-order pages
+          '/*?page=',      // avoid indexing deep pagination pages
+        ],
+      },
+      {
+        userAgent: 'GPTBot',
+        disallow: ['/'],    // block AI crawlers if desired
       },
     ],
     sitemap: `${siteUrl}/sitemap.xml`,
+    host: siteUrl,
   };
 }