HH-564: harden durable realtime publish boundaries (#139)

* fix(HH-564): harden durable realtime enqueue

* fix(HH-564): wire production SSE stream

---------

Co-authored-by: Rogee <rogee@ipao.vip>

backend/internal/worker/worker.go

@@ -317,14 +317,20 @@ func (wp *WorkerPool) persistJob(ctx context.Context, db *gorm.DB, jobType strin
 		}
 	}
 
-	if err := db.WithContext(ctx).Create(job).Error; err != nil {
-		if job.IdempotencyKey != "" {
-			var existing model.BackgroundJob
-			if findErr := db.WithContext(ctx).Where("idempotency_key = ?", job.IdempotencyKey).First(&existing).Error; findErr == nil {
-				return &existing, false, nil
-			}
+	query := db.WithContext(ctx)
+	if job.IdempotencyKey != "" {
+		query = query.Clauses(clause.OnConflict{DoNothing: true})
+	}
+	result := query.Create(job)
+	if result.Error != nil {
+		return nil, false, result.Error
+	}
+	if job.IdempotencyKey != "" && result.RowsAffected == 0 {
+		var existing model.BackgroundJob
+		if err := db.WithContext(ctx).Where("idempotency_key = ?", job.IdempotencyKey).First(&existing).Error; err != nil {
+			return nil, false, err
 		}
-		return nil, false, err
+		return &existing, false, nil
 	}
 	return job, true, nil
 }