e9e7e9dbac
- Implement backup package with SQLite VACUUM INTO for safe backups - Add scheduler with configurable interval (default: 24h) - Add retention policy with automatic cleanup (default: 7 days) - Add optional gzip compression (~10x size reduction) - Add comprehensive tests for backup creation and cleanup - Integrate backup scheduler in main.go with graceful shutdown - Add backup configuration variables (BACKUP_ENABLED, BACKUP_INTERVAL, BACKUP_RETENTION_DAYS, BACKUP_PATH, BACKUP_COMPRESS) - Backups run automatically in background goroutine - Coverage: backup package 52.7%