# Add Product Description Field for App Detail

## 1. Database Migration
We need to add a `description` column to the `products` table to store the product details.
**SQL Statement:**
```sql
ALTER TABLE products ADD COLUMN description TEXT COMMENT '商品详情';
```

## 2. Backend Model Update
Update the GORM model and DAO to reflect the database change.
*   **Model**: Update `internal/repository/mysql/model/products.gen.go` to include the `Description` field.
*   **DAO**: Update `internal/repository/mysql/dao/products.gen.go` to include the `Description` field definition and mapping.

## 3. Service Layer Update
Update `internal/service/product/product.go` to handle the new field.
*   **Input Structs**: Add `Description` to `CreateProductInput` and `ModifyProductInput`.
*   **Business Logic**:
    *   Update `CreateProduct` to save the description.
    *   Update `ModifyProduct` to update the description.
    *   Update `GetDetailForApp` to populate the `Description` field from the database instead of returning an empty string.

## 4. Admin API Update
Update the Admin API to allow creating and editing products with a description.
*   **File**: `internal/api/admin/product_create.go`
*   **Request Structs**: Add `description` field to `createProductRequest` and `modifyProductRequest`.
*   **Handlers**: Pass the `description` from the request to the service layer.

## 5. App API Verification
*   **File**: `internal/api/app/product.go`
*   The `GetProductDetailForApp` function already returns a `Description` field in the response. By updating the service layer to populate this field, the App API will automatically return the correct data.
