feat: add dynamic sitemap for Google Search Console indexing

- Generate sitemap.xml with all skill URLs for search engine discovery
- Return empty sitemap on mirror servers to prevent duplicate indexing

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

apps/web/app/sitemap.ts

@@ -0,0 +1,136 @@
+import type { MetadataRoute } from 'next';
+import { createDb, skillQueries, categoryQueries } from '@skillhub/db';
+
+const BASE_URL =
+  process.env.NEXT_PUBLIC_APP_URL || 'https://skills.palebluedot.live';
+
+const locales = ['en', 'fa'] as const;
+
+const staticRoutes = [
+  '',
+  '/browse',
+  '/categories',
+  '/featured',
+  '/new',
+  '/docs',
+  '/docs/getting-started',
+  '/docs/cli',
+  '/docs/api',
+  '/about',
+  '/attribution',
+  '/claude-plugin',
+  '/claim',
+  '/contact',
+  '/support',
+  '/terms',
+  '/privacy',
+];
+
+function makeEntry(
+  path: string,
+  options?: {
+    lastModified?: Date;
+    changeFrequency?: MetadataRoute.Sitemap[number]['changeFrequency'];
+    priority?: number;
+  }
+): MetadataRoute.Sitemap[number] {
+  return {
+    url: `${BASE_URL}${path}`,
+    lastModified: options?.lastModified,
+    changeFrequency: options?.changeFrequency,
+    priority: options?.priority,
+    alternates: {
+      languages: Object.fromEntries(
+        locales.map((locale) => {
+          // For root path, use /en or /fa; for others, prefix with locale
+          const localePath = path.replace(/^\/(en|fa)/, `/${locale}`);
+          return [locale, `${BASE_URL}${localePath}`];
+        })
+      ),
+    },
+  };
+}
+
+export default async function sitemap(): Promise<MetadataRoute.Sitemap> {
+  // Mirror servers should not serve a sitemap (robots.txt already blocks crawlers)
+  const isPrimary = process.env.IS_PRIMARY_SERVER !== 'false';
+  if (!isPrimary) {
+    return [];
+  }
+
+  const db = createDb();
+  const entries: MetadataRoute.Sitemap = [];
+
+  // Static pages (for each locale)
+  for (const locale of locales) {
+    for (const route of staticRoutes) {
+      const path = `/${locale}${route}`;
+      const isHome = route === '';
+      entries.push(
+        makeEntry(path, {
+          changeFrequency: isHome ? 'daily' : 'weekly',
+          priority: isHome ? 1.0 : 0.5,
+        })
+      );
+    }
+  }
+
+  // Dynamic: skill pages
+  try {
+    const allSkills = await skillQueries.getAllForSitemap(db);
+
+    for (const skill of allSkills) {
+      for (const locale of locales) {
+        entries.push(
+          makeEntry(`/${locale}/skill/${skill.id}`, {
+            lastModified: skill.updatedAt,
+            changeFrequency: 'weekly',
+            priority: 0.7,
+          })
+        );
+      }
+    }
+
+    // Dynamic: owner pages (unique owners from skills)
+    const uniqueOwners = new Map<string, Date>();
+    for (const skill of allSkills) {
+      const existing = uniqueOwners.get(skill.githubOwner);
+      if (!existing || skill.updatedAt > existing) {
+        uniqueOwners.set(skill.githubOwner, skill.updatedAt);
+      }
+    }
+
+    for (const [owner, lastModified] of uniqueOwners) {
+      for (const locale of locales) {
+        entries.push(
+          makeEntry(`/${locale}/owner/${owner}`, {
+            lastModified,
+            changeFrequency: 'weekly',
+            priority: 0.6,
+          })
+        );
+      }
+    }
+  } catch {
+    // If DB is unavailable, return static pages only
+  }
+
+  // Dynamic: category pages
+  try {
+    const allCategories = await categoryQueries.getAll(db);
+    for (const category of allCategories) {
+      for (const locale of locales) {
+        entries.push(
+          makeEntry(`/${locale}/browse?category=${category.slug}`, {
+            changeFrequency: 'weekly',
+            priority: 0.5,
+          })
+        );
+      }
+    }
+  } catch {
+    // If DB is unavailable, skip categories
+  }
+
+  return entries;
+}

packages/db/src/queries.ts

@@ -399,6 +399,20 @@ export const skillQueries = {
     return result[0]?.count ?? 0;
   },
 
+  /**
+   * Get all skills for sitemap generation (lightweight: id, updatedAt, githubOwner only)
+   */
+  getAllForSitemap: async (db: DB) => {
+    return db
+      .select({
+        id: skills.id,
+        updatedAt: skills.updatedAt,
+        githubOwner: skills.githubOwner,
+      })
+      .from(skills)
+      .where(and(eq(skills.isBlocked, false), eq(skills.sourceFormat, 'skill.md')));
+  },
+
   /**
    * Get site engagement level for adaptive algorithm
    * Returns: 'cold_start' | 'growth' | 'mature'