feat: add initial implementation of Kitchen CRM with authentication and dashboard features

- Create global styles and theme management
- Implement app shell layout with sidebar navigation
- Add authentication layout and pages for login and registration
- Develop dashboard page with placeholder content
- Introduce routing guards for guest-only and authenticated routes
- Set up Zustand for state management of authentication and theme
- Create API types and structures for CRM entities
- Configure Vite with PWA support and Tailwind CSS

frontend/src/App.tsx

@@ -0,0 +1,16 @@
+import { Suspense } from 'react'
+import { RouterProvider } from 'react-router-dom'
+
+import { AppProvider } from '@/app/providers/app-provider'
+import { AppLoading } from '@/components/system/app-loading'
+import { router } from '@/routes/router'
+
+const App = () => (
+  <AppProvider>
+    <Suspense fallback={<AppLoading />}>
+      <RouterProvider router={router} />
+    </Suspense>
+  </AppProvider>
+)
+
+export default App