test: add AddToCartButton and ToggleCartIcon integration tests, fix timer cleanup

client/src/shared/ui/__tests__/CartSnackbar.test.tsx

@@ -1,6 +1,6 @@
 import { render, screen, fireEvent, act } from '@testing-library/react'
 import { MemoryRouter } from 'react-router-dom'
-import { describe, it, expect, vi, beforeEach } from 'vitest'
+import { describe, it, expect, vi, beforeEach, afterEach } from 'vitest'
 import { cartAdded, cartDismissed } from '@/shared/model/cart-notifications'
 import { CartSnackbar } from '@/shared/ui/CartSnackbar'
 
@@ -15,6 +15,10 @@ beforeEach(() => {
   navigateMock.mockClear()
 })
 
+afterEach(() => {
+  vi.useRealTimers()
+})
+
 function renderWithRouter() {
   render(
     <MemoryRouter initialEntries={['/']}>
@@ -53,7 +57,6 @@ describe('CartSnackbar', () => {
       vi.advanceTimersByTime(4000)
     })
     expect(screen.queryByText(/товар добавлен/i)).not.toBeInTheDocument()
-    vi.useRealTimers()
   })
 
   it('navigates to /cart and closes on "Перейти в корзину" click', () => {