feat: implement UTC to IST timezone conversion across all system components
- Standardize all timestamps to use Indian Standard Time (IST, UTC+5:30)
- Add comprehensive timezone utilities and configuration
- Create database migration tools with safety features and rollback capability
- Update all models to use IST for created_at, updated_at, and temporal fields
- Implement timezone-aware OTP expiry and rate limiting
- Add real-time timezone documentation API endpoints
- Include extensive testing suite for timezone edge cases
- Create migration guides and API documentation