refactor: use robots and sitemap metadata

app/sitemap.ts

@@ -0,0 +1,18 @@
+import { MetadataRoute } from 'next'
+import { allBlogs } from 'contentlayer/generated'
+import siteMetadata from '@/data/siteMetadata'
+
+export default function sitemap(): MetadataRoute.Sitemap {
+  const siteUrl = siteMetadata.siteUrl
+  const blogRoutes = allBlogs.map((post) => ({
+    url: `${siteUrl}/${post.path}`,
+    lastModified: post.lastmod || post.date,
+  }))
+
+  const routes = ['', 'blog', 'projects', 'tags'].map((route) => ({
+    url: `${siteUrl}/${route}`,
+    lastModified: new Date().toISOString().split('T')[0],
+  }))
+
+  return [...routes, ...blogRoutes]
+}