docs: initialize project documentation

Adds the standard ./docs/ structure (overview, codebase summary,
architecture, code standards, design guidelines, deployment guide,
roadmap) and the code-review report under ./plans/reports/.
README now points at the docs and covers the codeserver dev profile.

web/README.md

@@ -2,14 +2,32 @@
 
 Bàn số của trò chơi "Lô tô" — Next.js app.
 
+Two pages: `/` for players, `/master` for the host (quản trò) — calls numbers, shows a tracking board, and has its own player card to play along.
+
+See `docs/` for project overview, architecture, code standards, and deployment.
+
 ## Development
 
 ```bash
 npm run dev
 ```
 
+### Inside code-server (reverse proxy)
+
+```bash
+cp .env.example .env.local
+# edit .env.local: set CODESERVER_HOST and CODESERVER_PORT
+npm run dev:codeserver
+```
+
+Open `https://<CODESERVER_HOST>/absproxy/<CODESERVER_PORT>/`.
+
+Use `/absproxy/{port}/`, **not** `/proxy/{port}/` — the latter strips the path prefix and breaks Next's `basePath`. HMR may not survive the proxy; refresh manually if it disconnects.
+
 ## Build
 
 ```bash
 npm run build
 ```
+
+Static export to `out/`. Deployed to GitHub Pages from `master` via `.github/workflows/deploy.yml`.