新增测试代码规范、修复响应体断言缺失与魔法数字

- AGENTS.md 新增测试代码专项规范：常量、fixture、触发器、HTTP断言、层边界说明
- TestUpdateAllocationExpiryBaseHTTP 补全 PATCH 响应体字段断言
- 四个集成测试文件以 testIDMask 局部常量替换 0x7fffffff 魔法数字

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

internal/task/auto_purchase_terms_integration_test.go

@@ -1,5 +1,8 @@
 package task
 
+// testIDMask 用于将纳秒时间戳截断为合法的 uint 主键范围，仅限测试用。
+const testIDMask = testIDMask
+
 import (
 	"context"
 	"strconv"
@@ -34,7 +37,7 @@ func TestAutoPurchasePersistsTermsSnapshotsAndRealnameDecision(t *testing.T) {
 			tx := testutil.NewPostgresTransaction(t)
 			card := createAutoPurchaseCard(t, tx, testCase.realnameStatus)
 			pkg := createAutoPurchasePackage(t, tx, constants.PackageTypeFormal, testCase.defaultBase, 31)
-			shopID := uint(time.Now().UnixNano() & 0x7fffffff)
+			shopID := uint(time.Now().UnixNano() & testIDMask)
 			if testCase.override != nil {
 				allocation := &model.ShopPackageAllocation{ShopID: shopID, PackageID: pkg.ID, CostPrice: 1, RetailPrice: 2, Status: constants.StatusEnabled, ShelfStatus: 1, ExpiryBaseOverride: testCase.override}
 				if err := tx.Create(allocation).Error; err != nil {
@@ -186,7 +189,7 @@ func createAutoPurchasePackage(t *testing.T, tx *gorm.DB, packageType, expiryBas
 }
 
 func newAutoPurchaseOrder(cardID uint, sellerShopID *uint) *model.Order {
-	orderID := uint(time.Now().UnixNano() & 0x7fffffff)
+	orderID := uint(time.Now().UnixNano() & testIDMask)
 	return &model.Order{Model: gorm.Model{ID: orderID}, OrderNo: "UR55-AUTO-" + strconv.FormatUint(uint64(orderID), 10), OrderType: model.OrderTypeSingleCard, IotCardID: &cardID, SellerShopID: sellerShopID, TotalAmount: 100, Generation: 1}
 }