fix: IAP 支付流程优化与关键 bug 修复

- getStatusLogic 类型断言修复（*user.User）
- restoreLogic 事务拆分为单条处理 + appAccountToken 解析
- attachTransactionLogic 提取 ParseProductIdDuration 共享函数
- 新增 config_helper.go 统一 Apple API 配置加载
- reconcileLogic 补充 BundleID 配置读取
- activateOrderLogic 邀请赠送天数逻辑完善

Co-Authored-By: claude-flow <ruv@ruv.net>

internal/types/types.go

@@ -130,8 +130,9 @@ type AttachAppleTransactionRequest struct {
 }
 
 type AttachAppleTransactionResponse struct {
-	ExpiresAt int64  `json:"expires_at"`
-	Tier      string `json:"tier"`
+	ExpiresAt       int64  `json:"expires_at"`
+	Tier            string `json:"tier"`
+	ExistingOrderNo string `json:"existing_order_no,omitempty"`
 }
 
 type AuthConfig struct {