feat: initialize project with Symfony, React, and Tailwind CSS setup

- Add package.json with development and production dependencies
- Create postcss.config.js for Tailwind CSS integration
- Implement AdminController for handling admin routes
- Add admin index template with React root element
- Create base template for consistent layout
- Configure TypeScript with tsconfig.json
- Set up Webpack configuration for asset management

assets/admin/index.tsx

@@ -0,0 +1,25 @@
+import React from 'react';
+import { createRoot } from 'react-dom/client';
+import { BrowserRouter } from 'react-router-dom';
+import { QueryClient, QueryClientProvider } from '@tanstack/react-query';
+import { Toaster } from 'sonner';
+import App from './App';
+import './styles.css';
+
+const queryClient = new QueryClient({
+  defaultOptions: {
+    queries: { retry: 1, staleTime: 30_000 },
+  },
+});
+
+const root = document.getElementById('admin-root')!;
+createRoot(root).render(
+  <React.StrictMode>
+    <QueryClientProvider client={queryClient}>
+      <BrowserRouter>
+        <App />
+        <Toaster position="top-left" richColors />
+      </BrowserRouter>
+    </QueryClientProvider>
+  </React.StrictMode>
+);