feat: 新增账户服务层，实现账户的增删改查及转账功能，并初始化AI记账、交易服务和预算仓库。

internal/repository/budget_repository.go

@@ -144,7 +144,13 @@ func (r *BudgetRepository) GetSpentAmount(budget *models.Budget, startDate, endD
 
 	// Filter by category if specified
 	if budget.CategoryID != nil {
-		query = query.Where("category_id = ?", *budget.CategoryID)
+		// Get sub-categories
+		var subCategoryIDs []uint
+		r.db.Model(&models.Category{}).Where("parent_id = ?", *budget.CategoryID).Pluck("id", &subCategoryIDs)
+
+		// Include the category itself and all its children
+		categoryIDs := append(subCategoryIDs, *budget.CategoryID)
+		query = query.Where("category_id IN ?", categoryIDs)
 	}
 
 	// Filter by account if specified