Add performance optimizations and database indexes

Database Indexes (migrations 006-009):
- Add case-insensitive indexes for auth lookups (email, username)
- Add composite indexes for task kanban queries
- Add indexes for notification, document, and completion queries
- Add unique index for active share codes
- Remove redundant idx_share_code_active and idx_notification_user_sent

Repository Optimizations:
- Add FindResidenceIDsByUser() lightweight method (IDs only, no preloads)
- Optimize GetResidenceUsers() with single UNION query (was 2 queries)
- Optimize kanban completion preloads to minimal columns (id, task_id, completed_at)

Service Optimizations:
- Remove Category/Priority/Frequency preloads from task queries
- Remove summary calculations from CRUD responses (client calculates)
- Use lightweight FindResidenceIDsByUser() instead of full FindByUser()

These changes reduce database load and response times for common operations.

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

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

internal/services/residence_service.go

@@ -136,23 +136,18 @@ func (s *ResidenceService) GetMyResidences(userID uint, now time.Time) (*respons
 // This is a lightweight endpoint for refreshing summary counts without full residence data.
 // The `now` parameter should be the start of day in the user's timezone for accurate overdue detection.
 func (s *ResidenceService) GetSummary(userID uint, now time.Time) (*responses.TotalSummary, error) {
-	residences, err := s.residenceRepo.FindByUser(userID)
+	// Get residence IDs (lightweight - no preloads)
+	residenceIDs, err := s.residenceRepo.FindResidenceIDsByUser(userID)
 	if err != nil {
 		return nil, err
 	}
 
 	summary := &responses.TotalSummary{
-		TotalResidences: len(residences),
+		TotalResidences: len(residenceIDs),
 	}
 
 	// Get task statistics if task repository is available
-	if s.taskRepo != nil && len(residences) > 0 {
-		// Collect residence IDs
-		residenceIDs := make([]uint, len(residences))
-		for i, r := range residences {
-			residenceIDs[i] = r.ID
-		}
-
+	if s.taskRepo != nil && len(residenceIDs) > 0 {
 		// Get aggregated statistics using user's timezone-aware time
 		stats, err := s.taskRepo.GetTaskStatistics(residenceIDs, now)
 		if err == nil && stats != nil {
@@ -167,14 +162,14 @@ func (s *ResidenceService) GetSummary(userID uint, now time.Time) (*responses.To
 	return summary, nil
 }
 
-// getSummaryForUser is a helper that returns summary for a user, or empty summary on error.
-// Uses UTC time. For timezone-aware summary, use GetSummary directly.
-func (s *ResidenceService) getSummaryForUser(userID uint) responses.TotalSummary {
-	summary, err := s.GetSummary(userID, time.Now().UTC())
-	if err != nil || summary == nil {
-		return responses.TotalSummary{}
-	}
-	return *summary
+// getSummaryForUser returns an empty summary placeholder.
+// DEPRECATED: Summary calculation has been removed from CRUD responses for performance.
+// Clients should calculate summary from kanban data instead (which already includes all tasks).
+// The summary field is kept in responses for backward compatibility but will always be empty.
+// For actual summary data, use GetSummary() directly or rely on my-residences/kanban endpoints.
+func (s *ResidenceService) getSummaryForUser(_ uint) responses.TotalSummary {
+	// Return empty summary - clients should calculate from kanban data
+	return responses.TotalSummary{}
 }
 
 // CreateResidence creates a new residence and returns it with updated summary