feat: migrate CartSnackbar to global notification store

client/src/app/App.tsx

@@ -1,7 +1,6 @@
 import { BrowserRouter } from 'react-router-dom'
 import { AppProviders } from '@/app/providers/AppProviders'
 import { AppRoutes } from '@/app/routes'
-import { CartSnackbar } from '@/shared/ui/CartSnackbar'
 import { NotificationStack } from '@/shared/ui/NotificationStack'
 import { ErrorBoundary } from '@/shared/ui/ErrorBoundary'
 import { NoiseOverlay } from '@/shared/ui/NoiseOverlay'
@@ -13,7 +12,6 @@ export function App() {
         <ErrorBoundary>
           <AppRoutes />
         </ErrorBoundary>
-        <CartSnackbar />
         <NotificationStack />
         <NoiseOverlay />
       </BrowserRouter>