Refactor media upload handling in MediaPanel: remove direct upload logic and integrate useUploadStore for file enqueueing. Update translations for upload status and add UploadSnackbar component to display upload notifications in the UI.

frontend/src/main.tsx

@@ -1,6 +1,6 @@
 import { StrictMode } from 'react'
 import { createRoot } from 'react-dom/client'
-import { QueryClient, QueryClientProvider } from '@tanstack/react-query'
+import { QueryClientProvider } from '@tanstack/react-query'
 import { RouterProvider } from '@tanstack/react-router'
 import './index.css'
 import './shared/lib/i18n'
@@ -8,6 +8,7 @@ import { ThemeProvider } from './theme/ThemeProvider'
 import { ToastProvider } from './shared/ui/toast-store'
 import { Toaster } from './shared/ui/toaster'
 import { router } from './router'
+import { queryClient } from './shared/api/query-client'
 import { setUnauthorizedHandler } from './shared/api/client'
 import { clearSession } from './features/auth/api'
 
@@ -15,8 +16,6 @@ import { clearSession } from './features/auth/api'
 // useRequireAuth/useRequireAdmin увидели user === null и сами увели на /login.
 setUnauthorizedHandler(clearSession)
 
-const queryClient = new QueryClient()
-
 createRoot(document.getElementById('root')!).render(
   <StrictMode>
     <QueryClientProvider client={queryClient}>