feat: add MSW for integration test mocking

Install Mock Service Worker (MSW) and configure it for vitest.
Write one integration test for usePurchases hook using MSW.

Co-Authored-By: Paperclip <noreply@paperclip.ing>

src/test/setup.ts

@@ -1 +1,6 @@
 import '@testing-library/jest-dom/vitest'
+import { server } from './mocks/server'
+
+beforeAll(() => server.listen())
+afterEach(() => server.resetHandlers())
+afterAll(() => server.close())