feat: initialize app with routing, query management, and UI framework

- Replace Vite boilerplate with React Router for page navigation
- Add React Query for server state and cache management
- Integrate shadcn/ui component library with Tailwind CSS v4
- Configure @/ path alias for clean module imports
- Set up Vite dev proxy to API backend
- Remove default App.css, App.tsx, and react.svg assets

src/components/layout/AppLayout.tsx

@@ -0,0 +1,9 @@
+import { Outlet } from "react-router-dom"
+
+export default function AppLayout() {
+  return (
+    <div className="min-h-screen">
+      <Outlet />
+    </div>
+  )
+}