getDueCardCount method
Lightweight count of due review cards (avoids fetching full objects).
Implementation
Future<int> getDueCardCount() async {
final userId = _client.auth.currentUser?.id;
if (userId == null) return 0;
final now = DateTime.now().toIso8601String();
final response = await _client
.from('review_cards')
.select('id')
.eq('user_id', userId)
.lte('next_review_at', now);
return (response as List<dynamic>).length;
}