Final production cleanup v3.0.0 - Remove development artifacts

Remove development tracking and migration files:
- persistence/ folder (development tracking only)
- MIGRATION_CHECKLIST.md (development artifact)
- READY_TO_MIGRATE.md (development artifact)

Production repository now contains only user-facing content.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

Author: ZenterFlow