feat: add deployment guide for chat app with frontend and backend instructions

Author: enjoy15

chat-app/README-deploy.md

@@ -0,0 +1,61 @@
+# Chat App Deployment Guide
+
+This project has a separate frontend and backend.
+
+## Project structure
+
+- `frontend/` — browser app served by a small Node server
+- `backend/` — Express API that stores messages in memory
+
+## Run locally
+
+### Backend
+
+```bash
+cd chat-app/backend
+npm install
+npm start
+```
+
+### Frontend
+
+```bash
+cd chat-app/frontend
+npm install
+npm start
+```
+
+## Environment variables
+
+The frontend needs the backend URL at runtime.
+
+- `API_BASE_URL` — backend public URL, for example:
+
+```text
+https://enjoy15-chat-app.hosting.codeyourfuture.io
+```
+
+If `API_BASE_URL` is not set, the frontend will try relative `/api` requests.
+
+## Deploying to Coolify
+
+Deploy the frontend and backend as separate services.
+
+### Frontend service
+
+- Root directory: `chat-app/frontend`
+- Use Nixpacks
+- Start command: `npm start`
+- Set environment variable: `API_BASE_URL=https://enjoy15-chat-app.hosting.codeyourfuture.io`
+
+### Backend service
+
+- Root directory: `chat-app/backend`
+- Use Nixpacks
+- Start command: `npm start`
+
+## Verification
+
+- Frontend should load and show messages
+- `https://enjoy15-chat-app-frontend.hosting.codeyourfuture.io/config.js` should contain the backend URL
+- `https://enjoy15-chat-app.hosting.codeyourfuture.io/api/messages` should return JSON