feat: add React frontend with search and mod pages

Add apps/web (Vite + React Router + Tailwind v4 + Zustand) with a search page and a mod page that analyzes saves via @tts/extract. Document the frontend in the README and docs.

apps/web/src/App.tsx

@@ -0,0 +1,28 @@
+import { Link, Route, Routes } from 'react-router-dom';
+import SearchPage from './pages/SearchPage';
+import ModPage from './pages/ModPage';
+
+export default function App() {
+  return (
+    <div className="min-h-screen bg-zinc-950 text-zinc-100">
+      <header className="border-b border-zinc-800">
+        <div className="mx-auto flex max-w-5xl items-center justify-between px-4 py-4">
+          <Link to="/" className="text-lg font-semibold tracking-tight">
+            TTS Workshop
+          </Link>
+          <nav className="flex gap-4 text-sm text-zinc-400">
+            <Link to="/" className="hover:text-zinc-100">
+              Search
+            </Link>
+          </nav>
+        </div>
+      </header>
+      <main className="mx-auto max-w-5xl px-4 py-8">
+        <Routes>
+          <Route path="/" element={<SearchPage />} />
+          <Route path="/mod/:id" element={<ModPage />} />
+        </Routes>
+      </main>
+    </div>
+  );
+}