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/domain/package/terms_test.go

@@ -9,15 +9,18 @@ import (
 
 // TestResolveTermsSnapshot 验证默认、覆盖及两种周期规则。
 func TestResolveTermsSnapshot(t *testing.T) {
-	override := constants.PackageExpiryBaseFromPurchase
+	overridePurchase := constants.PackageExpiryBaseFromPurchase
+	overrideActivation := constants.PackageExpiryBaseFromActivation
 	tests := []struct {
-		name       string
-		pkg        model.Package
-		allocation *model.ShopPackageAllocation
-		wantErr    bool
+		name            string
+		pkg             model.Package
+		allocation      *model.ShopPackageAllocation
+		wantErr         bool
+		wantExpiryBase  string
 	}{
-		{name: "自然月默认", pkg: model.Package{ExpiryBase: constants.PackageExpiryBaseFromActivation, CalendarType: constants.PackageCalendarTypeNaturalMonth, DurationMonths: 12}},
-		{name: "按天覆盖", pkg: model.Package{ExpiryBase: constants.PackageExpiryBaseFromActivation, CalendarType: constants.PackageCalendarTypeByDay, DurationDays: 30}, allocation: &model.ShopPackageAllocation{ExpiryBaseOverride: &override}},
+		{name: "自然月默认", pkg: model.Package{ExpiryBase: constants.PackageExpiryBaseFromActivation, CalendarType: constants.PackageCalendarTypeNaturalMonth, DurationMonths: 12}, wantExpiryBase: constants.PackageExpiryBaseFromActivation},
+		{name: "from_purchase 覆盖", pkg: model.Package{ExpiryBase: constants.PackageExpiryBaseFromActivation, CalendarType: constants.PackageCalendarTypeByDay, DurationDays: 30}, allocation: &model.ShopPackageAllocation{ExpiryBaseOverride: &overridePurchase}, wantExpiryBase: constants.PackageExpiryBaseFromPurchase},
+		{name: "from_activation 覆盖", pkg: model.Package{ExpiryBase: constants.PackageExpiryBaseFromPurchase, CalendarType: constants.PackageCalendarTypeByDay, DurationDays: 14}, allocation: &model.ShopPackageAllocation{ExpiryBaseOverride: &overrideActivation}, wantExpiryBase: constants.PackageExpiryBaseFromActivation},
 		{name: "非法生效条件", pkg: model.Package{ExpiryBase: "invalid", CalendarType: constants.PackageCalendarTypeByDay, DurationDays: 30}, wantErr: true},
 		{name: "非法按天时长", pkg: model.Package{ExpiryBase: constants.PackageExpiryBaseFromPurchase, CalendarType: constants.PackageCalendarTypeByDay}, wantErr: true},
 	}
@@ -30,6 +33,9 @@ func TestResolveTermsSnapshot(t *testing.T) {
 			if !test.wantErr && !got.IsValid() {
 				t.Fatalf("快照应有效：%+v", got)
 			}
+			if !test.wantErr && test.wantExpiryBase != "" && got.ExpiryBase != test.wantExpiryBase {
+				t.Fatalf("生效条件不符预期：want=%s got=%s", test.wantExpiryBase, got.ExpiryBase)
+			}
 		})
 	}
 }