Add HTTPS/SSL security configuration

- Update nginx config for HTTPS with Let's Encrypt certificates
- Add HTTP to HTTPS redirect
- Configure SSL security headers and HSTS
- Add Django HTTPS security settings for production
- Fix proxy_pass to use correct port 8081
- Enhance Content Security Policy for HTTPS

env-template.txt

@@ -14,6 +14,14 @@ DJANGO_ALLOWED_HOSTS=localhost,127.0.0.1
 # SECRET_KEY=your-production-secret-key-here
 # ALLOWED_HOSTS=your-domain.com,www.your-domain.com,localhost,127.0.0.1
 
+# HTTPS Security Settings (enable after SSL certificate is installed)
+# SECURE_SSL_REDIRECT=True
+# SESSION_COOKIE_SECURE=True
+# CSRF_COOKIE_SECURE=True
+# SECURE_HSTS_SECONDS=31536000
+# SECURE_HSTS_INCLUDE_SUBDOMAINS=True
+# SECURE_HSTS_PRELOAD=True
+
 LANGUAGE_CODE=de
 TIME_ZONE=Europe/Berlin