Add SSL/TLS support with Certbot and update deployment guide

- nginx/ssl.conf: full HTTPS config with HTTP→HTTPS redirect, modern TLS
  settings, HSTS header, and ACME challenge passthrough for renewals
- nginx/certbot-init.conf: minimal HTTP config for initial cert provisioning
- docker-compose.ssl.yml: compose override adding port 443, certbot volumes,
  and auto-renewal sidecar container
- docs/DEPLOYMENT.md: comprehensive 3-phase SSL walkthrough (obtain cert,
  enable SSL, auto-renewal) with day-to-day usage and revert instructions

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

nginx/certbot-init.conf

@@ -0,0 +1,18 @@
+# Temporary nginx config — used ONLY during the initial certbot certificate
+# request.  Once the cert is obtained, switch to ssl.conf and restart nginx.
+
+server {
+    listen 80;
+    server_name _;
+
+    # Certbot ACME challenge
+    location /.well-known/acme-challenge/ {
+        root /var/www/certbot;
+    }
+
+    # Return 503 for everything else so it's obvious this is not the real app
+    location / {
+        return 503 "SSL certificate is being provisioned. Try again in a minute.\n";
+        add_header Content-Type text/plain;
+    }
+}

nginx/ssl.conf

@@ -0,0 +1,106 @@
+upstream backend {
+    server backend:3000;
+}
+
+upstream frontend {
+    server frontend:5173;
+}
+
+# Redirect all HTTP to HTTPS
+server {
+    listen 80;
+    server_name _;
+
+    # Let certbot answer ACME challenges over HTTP
+    location /.well-known/acme-challenge/ {
+        root /var/www/certbot;
+    }
+
+    # Everything else -> HTTPS
+    location / {
+        return 301 https://$host$request_uri;
+    }
+}
+
+# HTTPS server
+server {
+    listen 443 ssl;
+    # Replace with your actual hostname:
+    server_name staging.example.com;
+
+    # --- TLS certificates (managed by certbot) ---
+    ssl_certificate     /etc/letsencrypt/live/staging.example.com/fullchain.pem;
+    ssl_certificate_key /etc/letsencrypt/live/staging.example.com/privkey.pem;
+
+    # --- Modern TLS settings ---
+    ssl_protocols TLSv1.2 TLSv1.3;
+    ssl_ciphers 'ECDHE-ECDSA-AES128-GCM-SHA256:ECDHE-RSA-AES128-GCM-SHA256:ECDHE-ECDSA-AES256-GCM-SHA384:ECDHE-RSA-AES256-GCM-SHA384';
+    ssl_prefer_server_ciphers on;
+    ssl_session_cache shared:SSL:10m;
+    ssl_session_timeout 1d;
+    ssl_session_tickets off;
+
+    # --- Security headers ---
+    add_header Strict-Transport-Security "max-age=63072000; includeSubDomains" always;
+    add_header X-Content-Type-Options nosniff always;
+    add_header X-Frame-Options SAMEORIGIN always;
+
+    # --- Proxy routes (same as default.conf) ---
+
+    # API requests -> NestJS backend
+    location /api/ {
+        proxy_pass http://backend;
+        proxy_http_version 1.1;
+        proxy_set_header Upgrade $http_upgrade;
+        proxy_set_header Connection 'upgrade';
+        proxy_set_header Host $host;
+        proxy_set_header X-Real-IP $remote_addr;
+        proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
+        proxy_set_header X-Forwarded-Proto $scheme;
+        proxy_cache_bypass $http_upgrade;
+    }
+
+    # AI recommendation endpoint needs a longer timeout (up to 3 minutes)
+    location /api/investment-planning/recommendations {
+        proxy_pass http://backend;
+        proxy_http_version 1.1;
+        proxy_set_header Upgrade $http_upgrade;
+        proxy_set_header Connection 'upgrade';
+        proxy_set_header Host $host;
+        proxy_set_header X-Real-IP $remote_addr;
+        proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
+        proxy_set_header X-Forwarded-Proto $scheme;
+        proxy_cache_bypass $http_upgrade;
+        proxy_read_timeout 180s;
+        proxy_connect_timeout 10s;
+        proxy_send_timeout 30s;
+    }
+
+    # AI health-score endpoint also needs a longer timeout
+    location /api/health-scores/calculate {
+        proxy_pass http://backend;
+        proxy_http_version 1.1;
+        proxy_set_header Upgrade $http_upgrade;
+        proxy_set_header Connection 'upgrade';
+        proxy_set_header Host $host;
+        proxy_set_header X-Real-IP $remote_addr;
+        proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
+        proxy_set_header X-Forwarded-Proto $scheme;
+        proxy_cache_bypass $http_upgrade;
+        proxy_read_timeout 180s;
+        proxy_connect_timeout 10s;
+        proxy_send_timeout 30s;
+    }
+
+    # Everything else -> Vite dev server (frontend)
+    location / {
+        proxy_pass http://frontend;
+        proxy_http_version 1.1;
+        proxy_set_header Upgrade $http_upgrade;
+        proxy_set_header Connection 'upgrade';
+        proxy_set_header Host $host;
+        proxy_set_header X-Real-IP $remote_addr;
+        proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
+        proxy_cache_bypass $http_upgrade;
+    }
+}