- Rename user_stats table to user_profile
- Split full_name into first_name and last_name columns
- Remove message_count (focus on profile data only)
- Add is_bot flag to track bot accounts
- Create migration.sql with automatic data migration and schema conversion
- Update MIGRATION.md with rename and migration instructions
- Update all DatabaseManager methods to use new table structure
- Update profile change detection to use separated name fields
