refactor(testing): migrate from Jest to Vitest for testing framework

vitest.config.ts

@@ -0,0 +1,12 @@
+import { defineConfig } from 'vitest/config';
+
+export default defineConfig({
+  test: {
+    globals: true,
+    environment: 'node',
+    include: ['__tests__/**/*.test.ts'],
+    coverage: {
+      reporter: ['text', 'json', 'html'],
+    },
+  },
+});