[Documentation] Add comprehensive production deployment guide

[VirtualAgentics]

Description

Expand the "Production Considerations" section with comprehensive deployment guidance, backend documentation, and operational procedures.

Background

The current README warns about in-memory limitations but lacks detailed production guidance. We need comprehensive documentation for production deployment.

Requirements

• Expand "Production Considerations" section in README
• Document concrete backends: pgvector, FAISS, Redis, Postgres
• Add sizing guidelines (QPS, corpus size, memory)
• Document HA topology: app + Redis + Postgres
• Add performance tuning guide
• Document backup and recovery procedures
• Add monitoring and alerting recommendations
• Provide architecture diagrams

Implementation Details

Files to modify:

• README.md - Expand production section
• docs/production/ - New production documentation
• docs/architecture/ - Architecture diagrams
• docs/operations/ - Operational procedures
• docs/performance/ - Performance tuning

Technical approach:

• Create comprehensive production guide
• Add backend-specific documentation
• Create architecture diagrams
• Document operational procedures
• Add performance tuning guides

Acceptance Criteria

• README has comprehensive production section
• All backends are documented
• Sizing guidelines are provided
• HA topology is documented
• Architecture diagrams are included

Testing Requirements

• Documentation review
• Link validation
• Example validation
• Accuracy review

Documentation Updates

• README.md - Production section
• Production guide - Comprehensive deployment
• Architecture docs - System design
• Operations docs - Procedures

Related Issues

• Depends on: P0 persistence, P0 sessions, P0 metrics
• Blocks: None