feat: configure Vitest testing framework

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

tests/setup.ts

@@ -0,0 +1,15 @@
+import { beforeAll, afterAll } from 'vitest';
+import dotenv from 'dotenv';
+
+// Load environment variables
+dotenv.config({ path: '.env' });
+
+beforeAll(async () => {
+  // Global test setup
+  console.log('Test suite starting...');
+});
+
+afterAll(async () => {
+  // Global test teardown
+  console.log('Test suite completed.');
+});