start method
void
start()
Start tracking a new session.
Implementation
void start() {
_reset();
_isTracking = true;
_startedAt = DateTime.now();
// Track time per state every second
_stateTimer = Timer.periodic(const Duration(seconds: 1), (_) {
_stateTimeSeconds[_currentState] =
(_stateTimeSeconds[_currentState] ?? 0) + 1;
});
notifyListeners();
}