修复 code review 问题：提取重复函数、补全缺失测试用例

- 提取 ResolveTermsFromTx 到 service/package，消除 order 和 auto_purchase 中的重复实现
- 补全 domain 测试：新增 from_activation 覆盖用例，现覆盖两种覆盖值
- 补全激活集成测试：新增 from_purchase 立即激活场景、历史记录兼容回退计数器验证
- 补全自动购包集成测试：新增购买后修改套餐配置不影响已有快照的验证

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

internal/service/package/activation_terms_integration_test.go

@@ -98,6 +98,69 @@ func TestRefundFollowUpActivatesNextPackageFromSnapshot(t *testing.T) {
 	}
 }
 
+// TestFromPurchaseActivatesImmediatelyAtPurchaseTime 验证 from_purchase 快照在购买时直接激活，不等实名。
+func TestFromPurchaseActivatesImmediatelyAtPurchaseTime(t *testing.T) {
+	tx := testutil.NewPostgresTransaction(t)
+	redisClient := testutil.NewRedisClient(t)
+	card := createActivationTermsCard(t, tx, constants.RealNameStatusNotVerified)
+	pkg := createActivationTermsPackage(t, tx, constants.PackageExpiryBaseFromPurchase, 7)
+	usage := createActivationTermsUsage(t, tx, pkg.ID, card.ID, 1, constants.PackageExpiryBaseFromPurchase, 7, false, time.Now())
+	service := NewActivationService(tx, redisClient, nil, nil, nil, zap.NewNop())
+	if err := service.ActivateSpecificPackage(context.Background(), usage.ID); err != nil {
+		t.Fatalf("from_purchase 直接激活失败：%v", err)
+	}
+	var refreshed model.PackageUsage
+	if err := tx.First(&refreshed, usage.ID).Error; err != nil {
+		t.Fatalf("查询激活结果失败：%v", err)
+	}
+	if refreshed.Status != constants.PackageUsageStatusActive || refreshed.ActivatedAt == nil || refreshed.ExpiresAt == nil {
+		t.Fatalf("from_purchase 套餐应已激活：status=%d activatedAt=%v expiresAt=%v", refreshed.Status, refreshed.ActivatedAt, refreshed.ExpiresAt)
+	}
+	if refreshed.PendingRealnameActivation {
+		t.Fatal("from_purchase 不应标记待实名")
+	}
+	expectedExpiry := CalculateExpiryTime(constants.PackageCalendarTypeByDay, *refreshed.ActivatedAt, 0, 7)
+	if !refreshed.ExpiresAt.Equal(expectedExpiry) {
+		t.Fatalf("to期时间不符：want=%v got=%v", expectedExpiry, refreshed.ExpiresAt)
+	}
+}
+
+// TestHistoricalFallbackFiresWarningAndIncrementsCounter 验证历史记录缺少快照时回退套餐当前配置并递增计数器。
+func TestHistoricalFallbackFiresWarningAndIncrementsCounter(t *testing.T) {
+	tx := testutil.NewPostgresTransaction(t)
+	redisClient := testutil.NewRedisClient(t)
+	card := createActivationTermsCard(t, tx, constants.RealNameStatusVerified)
+	pkg := createActivationTermsPackage(t, tx, constants.PackageExpiryBaseFromActivation, 21)
+	// 历史记录：四个快照字段全为空值/零值
+	unique := uint(time.Now().UnixNano() & 0x7fffffff)
+	usage := &model.PackageUsage{
+		OrderID: unique, OrderNo: "UR55-HIST-" + strconv.FormatUint(uint64(unique), 10),
+		PackageID: pkg.ID, PackageName: "UR55历史测试套餐",
+		UsageType: constants.AssetWalletResourceTypeIotCard, IotCardID: card.ID,
+		DataLimitMB: 1, Status: constants.PackageUsageStatusPending, Priority: 1, Generation: 1,
+		// 快照字段均留空，模拟 UR#55 上线前的旧数据
+	}
+	if err := tx.Omit("status").Create(usage).Error; err != nil {
+		t.Fatalf("创建历史测试使用记录失败：%v", err)
+	}
+	if err := tx.Model(usage).Update("status", constants.PackageUsageStatusPending).Error; err != nil {
+		t.Fatalf("设置历史测试状态失败：%v", err)
+	}
+	before := HistoricalTermsFallbackCount()
+	service := NewActivationService(tx, redisClient, nil, nil, nil, zap.NewNop())
+	if err := service.ActivateSpecificPackage(context.Background(), usage.ID); err != nil {
+		t.Fatalf("历史记录兼容激活失败：%v", err)
+	}
+	after := HistoricalTermsFallbackCount()
+	if after <= before {
+		t.Fatalf("历史回退计数器未递增：before=%d after=%d", before, after)
+	}
+	var refreshed model.PackageUsage
+	if err := tx.First(&refreshed, usage.ID).Error; err != nil || refreshed.Status != constants.PackageUsageStatusActive {
+		t.Fatalf("历史记录应兼容激活成功：status=%d err=%v", refreshed.Status, err)
+	}
+}
+
 // TestActivateSpecificPackageRejectsPartialSnapshot 验证新记录非法快照不会静默回退当前套餐配置。
 func TestActivateSpecificPackageRejectsPartialSnapshot(t *testing.T) {
 	tx := testutil.NewPostgresTransaction(t)