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/components/layout/AdminLayout.tsx

@@ -0,0 +1,18 @@
+import React from 'react';
+import { Outlet } from 'react-router-dom';
+import Sidebar from './Sidebar';
+import Topbar from './Topbar';
+
+export default function AdminLayout() {
+  return (
+    <div className="flex h-screen overflow-hidden bg-[#f1f5f9]">
+      <Sidebar />
+      <div className="flex flex-col flex-1 overflow-hidden">
+        <Topbar />
+        <main className="flex-1 overflow-y-auto p-6">
+          <Outlet />
+        </main>
+      </div>
+    </div>
+  );
+}