feat(seo): add build-time sitemap

app/sitemap.ts

@@ -0,0 +1,20 @@
+import type { MetadataRoute } from 'next'
+import { getAllTags, getPosts } from '@/lib/posts'
+import { tagToSlug } from '@/lib/tags'
+
+const siteUrl = process.env.NEXT_PUBLIC_SITE_URL || 'https://localhost:3000'
+
+export const dynamic = 'force-static'
+
+const absoluteUrl = (pathname: string): string => new URL(pathname, siteUrl).toString()
+
+const [posts, tags] = await Promise.all([getPosts(), getAllTags()])
+
+export default function sitemap(): MetadataRoute.Sitemap {
+  return [
+    { url: absoluteUrl('/') },
+    { url: absoluteUrl('/blog/') },
+    ...posts.map((post) => ({ url: absoluteUrl(`/blog/${post.slug}/`) })),
+    ...tags.map((tag) => ({ url: absoluteUrl(`/blog/tags/${tagToSlug(tag.label)}/`) })),
+  ]
+}