feat: 订单创建时快照买家手机号/昵称和套餐类型

新增字段：
- tb_order: buyer_phone, buyer_nickname（个人客户下单时快照）
- tb_order_item: package_type（套餐类型快照）

后台订单列表支持按 buyer_phone 精确过滤查询。

OpenSpec: order-buyer-snapshot

internal/model/order.go

@@ -18,8 +18,10 @@ type Order struct {
 	OrderType string `gorm:"column:order_type;type:varchar(20);not null;comment:订单类型 single_card-单卡购买 device-设备购买" json:"order_type"`
 
 	// 买家信息
-	BuyerType string `gorm:"column:buyer_type;type:varchar(20);not null;comment:买家类型 personal-个人客户 agent-代理商" json:"buyer_type"`
-	BuyerID   uint   `gorm:"column:buyer_id;index:idx_order_buyer;not null;comment:买家ID(个人客户ID或店铺ID)" json:"buyer_id"`
+	BuyerType     string  `gorm:"column:buyer_type;type:varchar(20);not null;comment:买家类型 personal-个人客户 agent-代理商" json:"buyer_type"`
+	BuyerID       uint    `gorm:"column:buyer_id;index:idx_order_buyer;not null;comment:买家ID(个人客户ID或店铺ID)" json:"buyer_id"`
+	BuyerPhone    *string `gorm:"column:buyer_phone;type:varchar(20);comment:下单时买家主手机号快照" json:"buyer_phone"`
+	BuyerNickname *string `gorm:"column:buyer_nickname;type:varchar(100);comment:下单时买家昵称快照" json:"buyer_nickname"`
 
 	// 关联资源
 	IotCardID       *uint  `gorm:"column:iot_card_id;index;comment:IoT卡ID(单卡购买时有值)" json:"iot_card_id,omitempty"`
@@ -121,12 +123,13 @@ type OrderItem struct {
 	gorm.Model
 	BaseModel `gorm:"embedded"`
 
-	OrderID     uint   `gorm:"column:order_id;index:idx_order_item_order_id;not null;comment:订单ID" json:"order_id"`
-	PackageID   uint   `gorm:"column:package_id;index;not null;comment:套餐ID" json:"package_id"`
-	PackageName string `gorm:"column:package_name;type:varchar(100);not null;comment:套餐名称(快照)" json:"package_name"`
-	Quantity    int    `gorm:"column:quantity;type:int;default:1;not null;comment:数量" json:"quantity"`
-	UnitPrice   int64  `gorm:"column:unit_price;type:bigint;not null;comment:单价(分)" json:"unit_price"`
-	Amount      int64  `gorm:"column:amount;type:bigint;not null;comment:小计金额(分)" json:"amount"`
+	OrderID     uint    `gorm:"column:order_id;index:idx_order_item_order_id;not null;comment:订单ID" json:"order_id"`
+	PackageID   uint    `gorm:"column:package_id;index;not null;comment:套餐ID" json:"package_id"`
+	PackageName string  `gorm:"column:package_name;type:varchar(100);not null;comment:套餐名称(快照)" json:"package_name"`
+	PackageType *string `gorm:"column:package_type;type:varchar(20);comment:套餐类型快照 formal-正式套餐 addon-加油包" json:"package_type"`
+	Quantity    int     `gorm:"column:quantity;type:int;default:1;not null;comment:数量" json:"quantity"`
+	UnitPrice   int64   `gorm:"column:unit_price;type:bigint;not null;comment:单价(分)" json:"unit_price"`
+	Amount      int64   `gorm:"column:amount;type:bigint;not null;comment:小计金额(分)" json:"amount"`
 }
 
 // TableName 指定表名