feat: moves getGitDate to a shared utils file

apps/blog/src/utils.ts

@@ -0,0 +1,10 @@
+import { execSync } from 'node:child_process';
+
+export function getGitDate(filePath: string): Date {
+  try {
+    const timestamp = execSync(`git log -1 --format=%cI -- "${filePath}"`, { encoding: 'utf8' }).trim();
+    return timestamp ? new Date(timestamp) : new Date(0);
+  } catch {
+    return new Date(0);
+  }
+}