fix: 修正套餐激活和时间字段nullable问题

核心变更：
1. Model层时间字段改为*time.Time并设为nullable
   - PackageUsage.ActivatedAt/ExpiresAt
   - PersonalCustomerDevice/ICCID/Phone.LastUsedAt/VerifiedAt

2. 数据库迁移：
   - activated_at/expires_at列移除NOT NULL约束
   - 清洗零值记录(status=0且activated_at<'2000-01-01')

3. 新增ActivateSpecificPackage方法：精准激活指定套餐，
   修复HandlePackageQueueActivation从"查找过期包"改为直接激活payload指定套餐

4. 新增孤儿套餐恢复扫描：Worker启动或每次套餐检查时，
   自动发现并恢复无status=1主套餐的孤儿载体

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

internal/service/package/activation_service.go

@@ -202,9 +202,13 @@ func (s *ActivationService) ActivateQueuedPackage(ctx context.Context, carrierTy
 				return errors.Wrap(errors.CodeDatabaseError, err, "更新过期主套餐状态失败")
 			}
 
+			expiresAt := now
+			if expiredMain.ExpiresAt != nil {
+				expiresAt = *expiredMain.ExpiresAt
+			}
 			s.logger.Info("主套餐已过期",
 				zap.Uint("usage_id", expiredMain.ID),
-				zap.Time("expires_at", expiredMain.ExpiresAt))
+				zap.Time("expires_at", expiresAt))
 
 			// 任务 9.7: 加油包级联失效
 			if err := s.invalidateAddons(ctx, tx, expiredMain.ID); err != nil {
@@ -221,6 +225,120 @@ func (s *ActivationService) ActivateQueuedPackage(ctx context.Context, carrierTy
 	})
 }
 
+// ActivateSpecificPackage 任务 4: 激活指定的套餐使用记录
+// 根据 PackageUsageID 精准激活目标套餐，而非重跑"查找过期包"流程
+func (s *ActivationService) ActivateSpecificPackage(ctx context.Context, packageUsageID uint) error {
+	// 加载 PackageUsage
+	var usage model.PackageUsage
+	if err := s.db.WithContext(ctx).First(&usage, packageUsageID).Error; err != nil {
+		if err == gorm.ErrRecordNotFound {
+			return errors.New(errors.CodeNotFound, "套餐使用记录不存在")
+		}
+		return errors.Wrap(errors.CodeDatabaseError, err, "查询套餐使用记录失败")
+	}
+
+	// 幂等检查：非待生效状态直接返回
+	if usage.Status != constants.PackageUsageStatusPending {
+		s.logger.Info("套餐无需激活（非待生效状态）",
+			zap.Uint("usage_id", usage.ID),
+			zap.Int("status", usage.Status))
+		return nil
+	}
+
+	// 确定载体类型和 ID
+	var carrierType string
+	var carrierID uint
+	if usage.IotCardID > 0 {
+		carrierType = "iot_card"
+		carrierID = usage.IotCardID
+	} else if usage.DeviceID > 0 {
+		carrierType = "device"
+		carrierID = usage.DeviceID
+	} else {
+		return errors.New(errors.CodeInvalidParam, "套餐使用记录缺少载体信息")
+	}
+
+	// 获取分布式锁
+	lockKey := constants.RedisPackageActivationLockKey(carrierType, carrierID)
+	lockValue := time.Now().String()
+	locked, err := s.redis.SetNX(ctx, lockKey, lockValue, 30*time.Second).Result()
+	if err != nil {
+		return errors.Wrap(errors.CodeRedisError, err, "获取分布式锁失败")
+	}
+	if !locked {
+		s.logger.Warn("套餐激活正在进行中，跳过",
+			zap.String("carrier_type", carrierType),
+			zap.Uint("carrier_id", carrierID))
+		return nil
+	}
+	defer s.redis.Del(ctx, lockKey)
+
+	// 加载关联 Package
+	var pkg model.Package
+	if err := s.db.WithContext(ctx).First(&pkg, usage.PackageID).Error; err != nil {
+		return errors.Wrap(errors.CodeDatabaseError, err, "查询套餐信息失败")
+	}
+
+	// 事务内激活
+	return s.db.WithContext(ctx).Transaction(func(tx *gorm.DB) error {
+		// 再次幂等检查（防止锁释放期间被其他操作激活）
+		var currentUsage model.PackageUsage
+		if err := tx.First(&currentUsage, packageUsageID).Error; err != nil {
+			return errors.Wrap(errors.CodeDatabaseError, err, "重新查询套餐使用记录失败")
+		}
+		if currentUsage.Status != constants.PackageUsageStatusPending {
+			return nil
+		}
+
+		// 按 ExpiryBase 选择激活时间基准
+		now := time.Now()
+		var activatedAt time.Time
+		if pkg.ExpiryBase == "from_purchase" {
+			activatedAt = usage.CreatedAt
+		} else {
+			activatedAt = now
+		}
+		expiresAt := CalculateExpiryTime(pkg.CalendarType, activatedAt, pkg.DurationMonths, pkg.DurationDays)
+		nextResetAt := CalculateNextResetTime(pkg.DataResetCycle, pkg.CalendarType, now, activatedAt)
+
+		// 更新套餐状态
+		updates := map[string]interface{}{
+			"status":       constants.PackageUsageStatusActive,
+			"activated_at": activatedAt,
+			"expires_at":   expiresAt,
+		}
+		if nextResetAt != nil {
+			updates["next_reset_at"] = *nextResetAt
+		}
+		if err := tx.Model(&usage).Updates(updates).Error; err != nil {
+			return errors.Wrap(errors.CodeDatabaseError, err, "激活套餐失败")
+		}
+
+		// 同步载体状态
+		s.syncCarrierStatusActivated(ctx, tx, &usage, carrierType, carrierID)
+
+		s.logger.Info("指定套餐已激活",
+			zap.Uint("usage_id", usage.ID),
+			zap.Uint("package_id", usage.PackageID),
+			zap.String("carrier_type", carrierType),
+			zap.Uint("carrier_id", carrierID))
+
+		// 异步复机
+		if s.resumeCallback != nil {
+			go func(ct string, cid uint) {
+				if err := s.resumeCallback.ResumeCardIfStopped(context.Background(), ct, cid); err != nil {
+					s.logger.Error("激活后自动复机失败",
+						zap.String("carrier_type", ct),
+						zap.Uint("carrier_id", cid),
+						zap.Error(err))
+				}
+			}(carrierType, carrierID)
+		}
+
+		return nil
+	})
+}
+
 // invalidateAddons 任务 9.7: 加油包级联失效
 func (s *ActivationService) invalidateAddons(ctx context.Context, tx *gorm.DB, masterUsageID uint) error {
 	var addons []*model.PackageUsage
@@ -280,7 +398,13 @@ func (s *ActivationService) activateNextMainPackage(ctx context.Context, tx *gor
 	}
 
 	// 激活套餐
-	activatedAt := now
+	// 按 ExpiryBase 选择激活计时基准：from_purchase-购买时起算用 CreatedAt，否则用当前时刻
+	var activatedAt time.Time
+	if pkg.ExpiryBase == "from_purchase" {
+		activatedAt = nextMain.CreatedAt
+	} else {
+		activatedAt = now
+	}
 	expiresAt := CalculateExpiryTime(pkg.CalendarType, activatedAt, pkg.DurationMonths, pkg.DurationDays)
 
 	// 计算下次重置时间