docs: add comprehensive refactoring and deployment guides

Comprehensive Guides Created:
1. MIGRATION_GUIDE.md (Type System Refactoring)
   - Step-by-step Organization type consolidation
   - 50+ file migration plan
   - Estimated 4-6 hours
   - Complete with examples and testing strategy

2. SERVICE_SPLITTING_GUIDE.md (Breaking Down Large Services)
   - How to split 1,000+ line service files
   - Complete examples for unified-llm.service.ts
   - Module extraction patterns
   - Testing strategies for each module

3. PRODUCTION_DEPLOYMENT_CHECKLIST.md (Launch Readiness)
   - Security (API key rotation)
   - Infrastructure setup (Supabase, Vercel)
   - Monitoring and logging
   - Rollback procedures
   - Post-launch monitoring plan

4. src/types/organization.ts (Centralized Types)
   - OrganizationSlug for identifiers
   - OrganizationEntity for full database entities
   - OrganizationRecord for Supabase tables
   - Complete type hierarchy with utilities

Benefits:
- Clear roadmap for all 3 requested refactoring tasks
- Production-ready deployment checklist
- Estimated time and difficulty for each task
- Working examples and code snippets
- Testing strategies included

Total Documentation: ~2,500 lines of actionable guidance

Author: claude