Crash fix (React Hooks violation):
- PlaybackTimeline.tsx: move ALL hooks (useRef for PanResponder, useCallback)
to before the early return; use seekRef/totalRef to share values into
PanResponder handlers without stale closure issues
Multiple recordings support:
- trainRecorder.ts: redesign to id-based multi-recording system
- RecordingMeta type for lightweight list (no snapshots)
- TrainRecording now includes id field
- saveRecording/loadRecordingById/deleteRecordingById/loadRecordingList
- migrateOldRecording() migrates old single MOCK_RECORDING key on first launch
- constants/storage.ts: add MOCK_RECORDINGS_INDEX + MOCK_RECORDING_DATA_PREFIX keys
- useTrainMenu: savedRecording → recordingList (RecordingMeta[]) + activeRecording (TrainRecording|null)
- startPlayback(id) loads full recording on demand
- deleteRecording(id) deletes by id and refreshes list
- stopPlayback clears activeRecording
- DataSourceSettings: recording list UI
- shows all recordings with date/time, snapshot count, duration
- ▶ play and 削除 buttons per row
- recording/playing status indicator
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>