feat(core): implement ProjectManager with Data Principle
- Create ProjectManager class enforcing Data Principle
- Implement ProjectData, SessionData, LootEvent dataclasses
- Add create_project, load_project, archive_project methods
- Implement session lifecycle (start_session, end_session)
- Add loot recording with auto-screenshot trigger (>50 PED)
- Include analytics: get_project_summary, compare_to_historical
- All PED calculations use Decimal for precision (Rule #4)
Every session is a Project: auto-saved, archivable, comparable.
28b8921efa