/// Whether a service's `day` field refers to the same calendar day as [day].
///
/// The backend returns ISO 8601 ("2026-07-13T00:00:00.000Z") while
/// `DateTime.toString()` produces a space separator ("2026-07-13 00:00:00.000Z"),
/// so comparing the two as raw strings never matched and every booked slot
/// rendered as free. Compare parsed calendar dates instead.
bool isSameServiceDay(DateTime day, String? serviceDay) {
  if (serviceDay == null || serviceDay.isEmpty) return false;
  final parsed = DateTime.tryParse(serviceDay);
  if (parsed == null) return false;
  return parsed.year == day.year &&
      parsed.month == day.month &&
      parsed.day == day.day;
}