Migrate server-rendered pages to React for / and /test

[Copilot]

This change converts the app’s user-facing pages to React while preserving the existing Express routes and API behavior. The goal is to make the app React-based without rewriting backend endpoint logic.

• React-rendered home page (GET /)

  • Replaced static HTML body content with a React root mount.
  • Added HomeApp React component rendered via ReactDOM.createRoot(...).

• React-rendered PATCH test page (GET /test)

  • Replaced inline DOM scripting with a React component (PatchTestApp).
  • Moved PATCH response display to React state (useState) instead of innerHTML mutation.

• Backend behavior unchanged

  • PATCH / and existing /silly* endpoints are unchanged.
  • Route wiring and Express structure remain intact.

function PatchTestApp() {
  const [result, setResult] = React.useState("");

  async function testPatch() {
    const response = await fetch("/", { method: "PATCH" });
    setResult("Response: " + (await response.text()));
  }

  return e("button", { className: "button", onClick: testPatch }, "Send PATCH Request");
}