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/vite.config.ts

@@ -0,0 +1,15 @@
+import { defineConfig } from 'vite';
+import react from '@vitejs/plugin-react';
+import tailwindcss from '@tailwindcss/vite';
+
+export default defineConfig({
+  plugins: [react(), tailwindcss()],
+  server: {
+    // Proxy API calls to the Hono backend during development.
+    proxy: {
+      '/search': 'http://localhost:3000',
+      '/items': 'http://localhost:3000',
+      '/health': 'http://localhost:3000',
+    },
+  },
+});