🔄 Add Comprehensive Backup Management System

✨ New Features:
- Complete backup lifecycle management (create, list, download, delete, cleanup)
- Web-based backup interface with real-time status updates
- Individual backup deletion and bulk cleanup for old backups
- Docker-aware backup operations with volume persistence
- Automated backup scheduling and retention policies

📁 Added Files:
- backup.py - Core backup script for creating timestamped archives
- docker_backup.sh - Docker-compatible backup wrapper script
- app/templates/backup.html - Web interface for backup management
- BACKUP_SYSTEM.md - Comprehensive backup system documentation
- BACKUP_GUIDE.md - Quick reference guide for backup operations

🔧 Enhanced Files:
- Dockerfile - Added backup.py copy for container availability
- docker-compose.yml - Added backup volume mount for persistence
- app/routes/api.py - Added backup API endpoints (create, list, delete, cleanup)
- app/routes/main.py - Added backup management route
- app/templates/index.html - Added backup management navigation
- README.md - Updated with backup system overview and quick start

🎯 Key Improvements:
- Fixed backup creation errors in Docker environment
- Added Docker-aware path detection for container operations
- Implemented proper error handling and user confirmation dialogs
- Added real-time backup status updates via JavaScript
- Enhanced data persistence with volume mounting

💡 Use Cases:
- Data protection and disaster recovery
- Environment migration and cloning
- Development data management
- Automated maintenance workflows

docker-compose.yml

@@ -45,6 +45,9 @@ services:
       
       # Application data - stores JSON databases (link_pages.json, qr_codes.json, short_urls.json)
       - /opt/qr/persistent:/app/data
+      
+      # Backup files - stores backup archives created by backup scripts
+      - ./backups:/app/backups
     
     # Health check configuration - monitors container health
     # Ensures the application is responding correctly