Enhance blog metadata and SEO with structured Open Graph data; add sitemap and robots.txt functionality; replace default OG image.

app/sitemap.tsx

@@ -0,0 +1,26 @@
+import { MetadataRoute } from "next";
+import { getSortedPostsData } from "@/lib/posts";
+
+export default function sitemap(): MetadataRoute.Sitemap {
+  const baseUrl = "https://blog.gabrielkaszewski.dev";
+
+  const posts = getSortedPostsData();
+
+  const postUrls = posts.map((post) => ({
+    url: `${baseUrl}/${post.id}`,
+    lastModified: new Date(post.date).toISOString(),
+    changeFrequency: "monthly" as const,
+    priority: 0.8,
+  }));
+
+  const staticUrls = [
+    {
+      url: baseUrl,
+      lastModified: new Date().toISOString(),
+      changeFrequency: "weekly" as const,
+      priority: 1.0,
+    },
+  ];
+
+  return [...staticUrls, ...postUrls];
+}