feat: Add enterprise DBA features for production reliability

New features implemented:

1. Backup Catalog (internal/catalog/)
   - SQLite-based backup tracking
   - Gap detection and RPO monitoring
   - Search and statistics
   - Filesystem sync

2. DR Drill Testing (internal/drill/)
   - Automated restore testing in Docker containers
   - Database validation with custom queries
   - Catalog integration for drill-tested status

3. Smart Notifications (internal/notify/)
   - Event batching with configurable intervals
   - Time-based escalation policies
   - HTML/text/Slack templates

4. Compliance Reports (internal/report/)
   - SOC2, GDPR, HIPAA, PCI-DSS, ISO27001 frameworks
   - Evidence collection from catalog
   - JSON, Markdown, HTML output formats

5. RTO/RPO Calculator (internal/rto/)
   - Recovery objective analysis
   - RTO breakdown by phase
   - Recommendations for improvement

6. Replica-Aware Backup (internal/replica/)
   - Topology detection for PostgreSQL/MySQL
   - Automatic replica selection
   - Configurable selection strategies

7. Parallel Table Backup (internal/parallel/)
   - Concurrent table dumps
   - Worker pool with progress tracking
   - Large table optimization

8. MySQL/MariaDB PITR (internal/pitr/)
   - Binary log parsing and replay
   - Point-in-time recovery support
   - Transaction filtering

CLI commands added: catalog, drill, report, rto

All changes support the goal: reliable 3 AM database recovery.

go.sum

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