chore: initial project scaffold with Fastify server and Vite React app

Set up monorepo structure with server/ (Fastify + TypeScript) and web/ (React + Vite + TypeScript).
Includes package configs, dev proxy setup, and mobile-first CSS foundation.

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

web/src/main.tsx

@@ -0,0 +1,10 @@
+import { StrictMode } from 'react';
+import { createRoot } from 'react-dom/client';
+import App from './App';
+import './index.css';
+
+createRoot(document.getElementById('root')!).render(
+  <StrictMode>
+    <App />
+  </StrictMode>,
+);