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/services/residence_service.go

@@ -113,6 +113,16 @@ func (s *ResidenceService) GetMyResidences(userID uint) (*responses.MyResidences
 			summary.TasksDueNextWeek = stats.TasksDueNextWeek
 			summary.TasksDueNextMonth = stats.TasksDueNextMonth
 		}
+
+		// Get per-residence overdue counts
+		overdueCounts, err := s.taskRepo.GetOverdueCountByResidence(residenceIDs)
+		if err == nil && overdueCounts != nil {
+			for i := range residenceResponses {
+				if count, ok := overdueCounts[residenceResponses[i].ID]; ok {
+					residenceResponses[i].OverdueCount = count
+				}
+			}
+		}
 	}
 
 	return &responses.MyResidencesResponse{