Final: Complete modernization - Option 1 deployment, unified persistence, migration scripts

- Implement Docker image-based deployment (Option 1)
  * Code immutable in image, no volume override
  * Eliminated init-data.sh manual step
  * Simplified deployment process

- Unified persistence in data/ folder
  * Moved nginx.conf and nginx-custom-domains.conf to data/
  * All runtime configs and data in single location
  * Clear separation: repo (source) vs data/ (runtime)

- Archive legacy features
  * Groups blueprint and templates removed
  * Legacy playlist routes redirected to content area
  * Organized in old_code_documentation/

- Added network migration support
  * New migrate_network.sh script for IP changes
  * Regenerates SSL certs for new IP
  * Updates database configuration
  * Tested workflow: clone → deploy → migrate

- Enhanced deploy.sh
  * Creates data directories
  * Copies nginx configs from repo to data/
  * Validates file existence before deployment
  * Prevents incomplete deployments

- Updated documentation
  * QUICK_DEPLOYMENT.md shows 4-step workflow
  * Complete deployment workflow documented
  * Migration procedures included

- Production ready deployment workflow:
  1. Clone & setup (.env configuration)
  2. Deploy (./deploy.sh)
  3. Migrate network (./migrate_network.sh if needed)
  4. Normal operations (docker compose restart)

app/blueprints/admin.py

@@ -8,7 +8,7 @@ from datetime import datetime
 from typing import Optional
 
 from app.extensions import db, bcrypt
-from app.models import User, Player, Group, Content, ServerLog, Playlist, HTTPSConfig
+from app.models import User, Player, 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