feat: complete nginx migration from caddy

- Replace Caddy reverse proxy with Nginx (nginx:alpine)
- Add nginx.conf with HTTP/HTTPS, gzip, and proxy settings
- Add nginx-custom-domains.conf template for custom domains
- Update docker-compose.yml to use Nginx service
- Add ProxyFix middleware to Flask app for proper header handling
- Create nginx_config_reader.py utility to read Nginx configuration
- Update admin blueprint to display Nginx status in https_config page
- Add Nginx configuration display to https_config.html template
- Generate self-signed SSL certificates for localhost
- Add utility scripts: generate_nginx_certs.sh
- Add documentation: NGINX_SETUP_QUICK.md, PROXY_FIX_SETUP.md
- All containers now running, HTTPS working, HTTP redirects to HTTPS
- Session cookies marked as Secure
- Security headers properly configured

app/blueprints/admin.py

@@ -11,6 +11,7 @@ from app.extensions import db, bcrypt
 from app.models import User, Player, Group, Content, ServerLog, Playlist, HTTPSConfig
 from app.utils.logger import log_action
 from app.utils.caddy_manager import CaddyConfigGenerator
+from app.utils.nginx_config_reader import get_nginx_status
 
 admin_bp = Blueprint('admin', __name__, url_prefix='/admin')
 
@@ -870,10 +871,14 @@ def https_config():
             db.session.commit()
             log_action('info', f'HTTPS status auto-corrected to enabled (detected from request)')
         
+        # Get Nginx configuration status
+        nginx_status = get_nginx_status()
+        
         return render_template('admin/https_config.html',
                              config=config,
                              is_https_active=is_https_active,
-                             current_host=current_host)
+                             current_host=current_host,
+                             nginx_status=nginx_status)
     except Exception as e:
         log_action('error', f'Error loading HTTPS config page: {str(e)}')
         flash('Error loading HTTPS configuration page.', 'danger')