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/sitemap.ts

@@ -1,32 +1,87 @@
 import type { MetadataRoute } from 'next';
+import { locales } from '@/i18n/config';
+import { fetchActiveListings } from '@/lib/listings-server';
 
-export default function sitemap(): MetadataRoute.Sitemap {
-  const siteUrl = process.env['NEXT_PUBLIC_SITE_URL'] || 'https://goodgo.vn';
+const siteUrl = process.env['NEXT_PUBLIC_SITE_URL'] || 'https://goodgo.vn';
 
-  return [
-    {
-      url: siteUrl,
-      lastModified: new Date(),
-      changeFrequency: 'daily',
-      priority: 1,
-    },
-    {
-      url: `${siteUrl}/search`,
-      lastModified: new Date(),
-      changeFrequency: 'daily',
-      priority: 0.9,
-    },
-    {
-      url: `${siteUrl}/login`,
-      lastModified: new Date(),
-      changeFrequency: 'monthly',
-      priority: 0.3,
-    },
-    {
-      url: `${siteUrl}/register`,
-      lastModified: new Date(),
-      changeFrequency: 'monthly',
-      priority: 0.3,
-    },
-  ];
+/**
+ * Dynamic sitemap that includes:
+ *  - Static pages (home, search, login, register) per locale
+ *  - All active property listings per locale
+ *
+ * ISR: the server-side fetch in fetchActiveListings uses `next: { revalidate: 3600 }`
+ * so the sitemap is regenerated roughly every hour.
+ */
+export default async function sitemap(): Promise<MetadataRoute.Sitemap> {
+  // ------------------------------------------------------------------
+  // 1. Static pages
+  // ------------------------------------------------------------------
+  const staticRoutes: MetadataRoute.Sitemap = [];
+
+  for (const locale of locales) {
+    staticRoutes.push(
+      {
+        url: `${siteUrl}/${locale}`,
+        lastModified: new Date(),
+        changeFrequency: 'daily',
+        priority: 1,
+      },
+      {
+        url: `${siteUrl}/${locale}/search`,
+        lastModified: new Date(),
+        changeFrequency: 'daily',
+        priority: 0.9,
+      },
+      {
+        url: `${siteUrl}/${locale}/login`,
+        lastModified: new Date(),
+        changeFrequency: 'monthly',
+        priority: 0.3,
+      },
+      {
+        url: `${siteUrl}/${locale}/register`,
+        lastModified: new Date(),
+        changeFrequency: 'monthly',
+        priority: 0.3,
+      },
+    );
+  }
+
+  // ------------------------------------------------------------------
+  // 2. Dynamic listing pages
+  // ------------------------------------------------------------------
+  const listingRoutes: MetadataRoute.Sitemap = [];
+
+  try {
+    // Fetch up to 1000 listings per page, paginate if needed.
+    // For very large catalogs this could be split into multiple sitemap
+    // indices, but for the current scale (<50k) a single file is fine.
+    let page = 1;
+    let totalPages = 1;
+
+    do {
+      const result = await fetchActiveListings({ page, limit: 1000 });
+      totalPages = result.totalPages;
+
+      for (const listing of result.data) {
+        for (const locale of locales) {
+          listingRoutes.push({
+            url: `${siteUrl}/${locale}/listings/${listing.id}`,
+            lastModified: listing.publishedAt
+              ? new Date(listing.publishedAt)
+              : new Date(listing.createdAt),
+            changeFrequency: 'weekly',
+            priority: 0.8,
+          });
+        }
+      }
+
+      page++;
+    } while (page <= totalPages);
+  } catch {
+    // If the API is unreachable, return static pages only.
+    // The sitemap will be retried on the next request (ISR).
+  }
+
+  return [...staticRoutes, ...listingRoutes];
 }