Implement testing framework with Vitest, add unit tests for API routes and utility functions, and configure CI workflow for automated testing. Update package dependencies for testing libraries and add test scripts to package.json.

lib/utils.ts

@@ -33,3 +33,9 @@ export function extractYouTubeId(url: string): string | null {
 export function isValidYouTubeId(id: string): boolean {
   return /^[A-Za-z0-9_-]{11}$/.test(id);
 }
+
+export function formatDuration(seconds: number): string {
+  const mins = Math.floor(seconds / 60);
+  const secs = Math.floor(seconds % 60);
+  return `${mins}:${secs.toString().padStart(2, '0')}`;
+}