Nginx Reverse Proxy: Front an App, Keep the Host Header

A backend app listens on http://127.0.0.1:<port> (local only). Put nginx in front of it as a reverse proxy. Write a server block under /etc/nginx/ so that:

• requests to /api/ are proxied to the backend (proxy_pass)
• the backend receives the original Host header (proxy_set_header Host $host;) — it routes by Host
• everything else (/) is served as static files from the docroot
• the server answers for the given server_name on port 80

The backend port, server name, and docroot for this session are in /root/brief.txt. Grading reads the config — it does not start nginx (on a live host you'd run nginx -t then systemctl reload nginx).