fix(用户): 修复删除用户软删除钩子

避免软删除钩子类型断言失败导致 500\n删除无记录时返回未找到错误并记录日志

backend/internal/service/admin_service.go

@@ -366,7 +366,11 @@ func (s *adminServiceImpl) DeleteUser(ctx context.Context, id int64) error {
 	if user.Role == "admin" {
 		return errors.New("cannot delete admin user")
 	}
-	return s.userRepo.Delete(ctx, id)
+	if err := s.userRepo.Delete(ctx, id); err != nil {
+		log.Printf("delete user failed: user_id=%d err=%v", id, err)
+		return err
+	}
+	return nil
 }
 
 func (s *adminServiceImpl) UpdateUserBalance(ctx context.Context, userID int64, balance float64, operation string, notes string) (*User, error) {