মডিউল ৪: Server Block, Domain, SSL

            ┌──────────────── Nginx ────────────────┐
 :80/:443 ──┤ server_name api.example.com → :8080   │──▶ Go API
            │ server_name app.example.com → :3000   │──▶ Next.js
            └───────────────────────────────────────┘

server {
    listen 80;
    server_name api.example.com;
    location / { proxy_pass http://127.0.0.1:8080; }
}
 
server {
    listen 80;
    server_name app.example.com;
    location / { proxy_pass http://127.0.0.1:3000; }
}

 ┌─────────────────────────┐        ┌──────────────────────────────┐
 │ server block #1 (:80)   │        │ server block #2 (:443 ssl)   │
 │ কাজ: HTTPS-এ redirect   │ ─301─▶ │ কাজ: আসল app serve করা       │
 └─────────────────────────┘        └──────────────────────────────┘

server {
    listen 80;
    server_name app.example.com;
    return 301 https://$host$request_uri;   # সব HTTP → HTTPS
}

 http://app.example.com/login
        │  301 Moved Permanently
        ▼
 https://app.example.com/login

 Browser ══(encrypted HTTPS)══▶ Nginx ──(plain HTTP)──▶ backend app
          🔒 TLS এখানে শেষ          🔓 internal network

server {
    listen 443 ssl http2;
    server_name api.example.com;
 
    ssl_certificate     /etc/letsencrypt/live/api.example.com/fullchain.pem;
    ssl_certificate_key /etc/letsencrypt/live/api.example.com/privkey.pem;
 
    location / {
        proxy_pass http://127.0.0.1:8080;
        proxy_set_header Host              $host;
        proxy_set_header X-Forwarded-Proto $scheme;
        proxy_set_header X-Forwarded-For   $proxy_add_x_forwarded_for;
    }
}

 [1] DNS: domain ──▶ VPS IP
       │
 [2] Nginx: server_name domain listen করছে
       │
 [3] Certbot: certificate issue (domain ownership verify)
       │
 [4] Nginx config-এ cert path বসে
       │
 [5] Renewal automate (cron/timer)

 Browser ══HTTPS══▶ Nginx ──┬─▶ Laravel  (PHP-FPM)
                            ├─▶ Go app
                            └─▶ Next.js