/// Time helpers. KST default. ISO 8601 string for DB storage.
DateTime nowKst() => DateTime.now().toLocal();

/// Strip time → YYYY-MM-DD (DB date column).
String dateOnly(DateTime d) {
  final local = d.toLocal();
  return '${local.year.toString().padLeft(4, '0')}-'
      '${local.month.toString().padLeft(2, '0')}-'
      '${local.day.toString().padLeft(2, '0')}';
}

/// Monday 00:00 of the week containing [d].
DateTime weekStart(DateTime d) {
  final local = d.toLocal();
  final mondayOffset = (local.weekday - DateTime.monday) % 7;
  final monday = DateTime(local.year, local.month, local.day)
      .subtract(Duration(days: mondayOffset));
  return monday;
}