feat(web): scaffold Vite + React + TS SPA with Vitest

Bootstraps the web/ SPA: Vite 6 + React 19 + TypeScript 5.8, Vitest
with jsdom, @testing-library/react, and a green smoke test asserting
the App renders its Collection heading.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

web/src/main.tsx

@@ -0,0 +1,9 @@
+import { StrictMode } from "react";
+import { createRoot } from "react-dom/client";
+import { App } from "./app";
+
+createRoot(document.getElementById("root")!).render(
+  <StrictMode>
+    <App />
+  </StrictMode>,
+);