- Add tests/test_json_file.py with unit tests for JsonFileRoomStorage and JsonFileTrackingStorage
- Reorganize data directories per han's feedback:
- Rooms: ~/.jigaido/data/room/<room_id>.json (was ~/.jigaido/data/<room_id>.json)
- Tracking: ~/.jigaido/data/tracking/<room_id>_<user_id>.json (was ~/.jigaido/tracking/...)
- Note: duplicate tracking is handled at TrackingService layer (returns False if already tracking), adapter allows duplicates by design