Render home page via React in Express app

[Copilot]

This updates the app to serve a React-based UI on the main route instead of hardcoded static HTML content. The home page keeps the same content, styling, and navigation while switching rendering to React.

• Home route migration to React

  • Replaced inline static markup in GET / with a React mount point (#root).
  • Added React and ReactDOM UMD scripts and rendered the existing homepage content through a React component.

• Behavior preserved

  • Kept all existing server endpoints and route structure unchanged (/, /test, patch/silly routes).
  • Kept the same visual design and CTA link to /test.

<div id="root"></div>
<script crossorigin src="https://unpkg.com/react@18/umd/react.production.min.js"></script>
<script crossorigin src="https://unpkg.com/react-dom@18/umd/react-dom.production.min.js"></script>
<script>
  const App = () =>
    React.createElement("div", { className: "container" },
      React.createElement("h1", null, "Welcome to Simple Server")
    );

  ReactDOM.createRoot(document.getElementById("root")).render(React.createElement(App));
</script>