fix(api): Fix S3 backup path-style configuration and improve UX.

- Fix critical S3 client configuration bug for path-style addressing
- Add toast notifications for better user feedback on S3 config operations
- Set up Toaster component in root layout for app-wide notifications
- Clean up unused imports in test files

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

frontend/src/routes/__root.tsx

@@ -5,6 +5,7 @@ import { PWAInstallPrompt, PWAUpdatePrompt } from "../components/PWAPrompts";
 import { usePWA } from "../hooks/usePWA";
 import { useVersionCheck } from "../hooks/useVersionCheck";
 import { SidebarInset, SidebarProvider } from "../components/ui/sidebar";
+import { Toaster } from "../components/ui/sonner";
 
 function RootLayout() {
   const { updateAvailable, updateSW, forceReload } = usePWA();
@@ -48,6 +49,9 @@ function RootLayout() {
         updateAvailable={updateAvailable}
         onUpdate={handlePWAUpdate}
       />
+
+      {/* Toast Notifications */}
+      <Toaster />
     </SidebarProvider>
   );
 }