chore: add vitest project config and yarn constraints

packages/booking-flow/vitest.config.ts

@@ -0,0 +1,9 @@
+import { defineConfig } from "vitest/config"
+
+export default defineConfig({
+  test: {
+    globals: true,
+    environment: "jsdom",
+    setupFiles: ["./vitest-setup.ts"],
+  },
+})