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.

README.md

@@ -7,6 +7,7 @@ analyze their contents. A lightweight, client-only pnpm monorepo.
 
 | Package             | Role                                                   | Runtime    |
 | ------------------- | ------------------------------------------------------ | ---------- |
+| `apps/web`          | React frontend: search + mod pages                     | Browser    |
 | `apps/proxy`        | Hono HTTP server: Workshop search + save fetch         | Node       |
 | `packages/tts`      | Fetch save from Steam, BSON-parse to `TTSMod`          | Node       |
 | `packages/extract`  | Analyze a `TTSMod`: objects, asset refs, downloads     | Isomorphic |
@@ -25,6 +26,10 @@ pnpm dev               # runs the proxy at http://localhost:3000
 
 Get a Steam Web API key at https://steamcommunity.com/dev/apikey (free).
 
+To run the frontend alongside the proxy, open a second terminal and run
+`pnpm --filter @tts/web dev` (serves at http://localhost:5173 and proxies
+`/search`, `/items`, and `/health` to the backend).
+
 ## API
 
 | Method | Path              | Description                                  |
@@ -38,6 +43,7 @@ Get a Steam Web API key at https://steamcommunity.com/dev/apikey (free).
 
 ```sh
 pnpm dev          # run the proxy (tsx watch)
+pnpm dev:web      # run the frontend (vite)
 pnpm build        # compile all packages
 pnpm typecheck    # typecheck all packages
 pnpm test         # run the unit tests (vitest)