Document CDC Sink ongoing task

[ayende]

CDC Sink Documentation

Adds comprehensive documentation for the CDC (Change Data Capture) Sink ongoing task feature.

Changes

• Overview & Architecture: Added overview, how-it-works, and schema design guides
• Configuration: Added API reference, configuration reference, and server configuration docs
• Features: Documented column mapping, attachment handling, property retention, delete strategies, and patching
• Deployment: Added guides for linked tables, embedded tables, failover, and consistency
• PostgreSQL Integration: Complete PostgreSQL setup including replica identity, WAL configuration, permissions, monitoring, and cleanup
• SQL Server Integration: Basic overview for SQL Server support
• Examples: Four example scenarios covering simple migration, event sourcing, denormalization, and complex nesting
• Operations: Guides for monitoring, troubleshooting, and maintenance

35 new documentation files with ~4600 lines of content.