- Add timestamp field to ProcessedGpsData with copyWith support
- Add precision switching thresholds: 3.33 m/s (12 km/h) up, 2.22 m/s (8 km/h) down
- Add PRECISION_SWITCH_FIRST_FIX_DELAY (5s) to prevent early switching
- Add BACKGROUND_GRACE_PERIOD (7s) for lifecycle-aware GPS management
- Mark GPS_GRACE_PERIOD as deprecated in favor of BACKGROUND_GRACE_PERIOD
- Change GpsService.positionStream to createPositionStream() with dynamic accuracy
- Keep deprecated positionStream getter for backward compatibility
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>