Add per-residence overdue_count to API response

Adds overdueCount field to each residence in my-residences endpoint,
enabling the mobile app to show pulsing icons on individual residence
cards that have overdue tasks.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

internal/repositories/task_repo.go

@@ -502,3 +502,37 @@ func (r *TaskRepository) GetTaskStatistics(residenceIDs []uint) (*TaskStatistics
 		TasksDueNextMonth: int(tasksDueNextMonth),
 	}, nil
 }
+
+// GetOverdueCountByResidence returns a map of residence ID to overdue task count.
+// Uses the task.scopes package for consistent filtering logic.
+func (r *TaskRepository) GetOverdueCountByResidence(residenceIDs []uint) (map[uint]int, error) {
+	if len(residenceIDs) == 0 {
+		return map[uint]int{}, nil
+	}
+
+	now := time.Now().UTC()
+
+	// Query to get overdue count grouped by residence
+	type result struct {
+		ResidenceID uint
+		Count       int64
+	}
+	var results []result
+
+	err := r.db.Model(&models.Task{}).
+		Select("residence_id, COUNT(*) as count").
+		Scopes(task.ScopeForResidences(residenceIDs), task.ScopeOverdue(now)).
+		Group("residence_id").
+		Scan(&results).Error
+	if err != nil {
+		return nil, err
+	}
+
+	// Convert to map
+	countMap := make(map[uint]int)
+	for _, r := range results {
+		countMap[r.ResidenceID] = int(r.Count)
+	}
+
+	return countMap, nil
+}