style: 修复 gofmt 格式化问题

格式化以下测试文件以符合 Go 代码风格规范：
- fixtures_integration_test.go
- user_repo_integration_test.go
- api_key_service_delete_test.go

backend/internal/repository/fixtures_integration_test.go

@@ -390,4 +390,3 @@ func mustBindAccountToGroup(t *testing.T, client *dbent.Client, accountID, group
 		Save(ctx)
 	require.NoError(t, err, "create account_group")
 }
-

backend/internal/repository/user_repo_integration_test.go

@@ -76,8 +76,8 @@ func (s *UserRepoSuite) mustCreateSubscription(userID, groupID int64, mutate fun
 	create := s.client.UserSubscription.Create().
 		SetUserID(userID).
 		SetGroupID(groupID).
-		SetStartsAt(now.Add(-1*time.Hour)).
-		SetExpiresAt(now.Add(24*time.Hour)).
+		SetStartsAt(now.Add(-1 * time.Hour)).
+		SetExpiresAt(now.Add(24 * time.Hour)).
 		SetStatus(service.SubscriptionStatusActive).
 		SetAssignedAt(now).
 		SetNotes("")
@@ -507,4 +507,3 @@ func (s *UserRepoSuite) TestCRUD_And_Filters_And_AtomicUpdates() {
 	s.Require().Len(users, 1, "ListWithFilters len mismatch")
 	s.Require().Equal(user2.ID, users[0].ID, "ListWithFilters result mismatch")
 }
-

backend/internal/service/api_key_service_delete_test.go

@@ -146,8 +146,8 @@ func TestApiKeyService_Delete_OwnerMismatch(t *testing.T) {
 
 	err := svc.Delete(context.Background(), 10, 2) // API Key ID=10, 调用者 userID=2
 	require.ErrorIs(t, err, ErrInsufficientPerms)
-	require.Empty(t, repo.deletedIDs)    // 验证删除操作未被调用
-	require.Empty(t, cache.invalidated)  // 验证缓存未被清除
+	require.Empty(t, repo.deletedIDs)   // 验证删除操作未被调用
+	require.Empty(t, cache.invalidated) // 验证缓存未被清除
 }
 
 // TestApiKeyService_Delete_Success 测试所有者成功删除 API Key 的场景。
@@ -164,7 +164,7 @@ func TestApiKeyService_Delete_Success(t *testing.T) {
 
 	err := svc.Delete(context.Background(), 42, 7) // API Key ID=42, 调用者 userID=7
 	require.NoError(t, err)
-	require.Equal(t, []int64{42}, repo.deletedIDs) // 验证正确的 API Key 被删除
+	require.Equal(t, []int64{42}, repo.deletedIDs)  // 验证正确的 API Key 被删除
 	require.Equal(t, []int64{7}, cache.invalidated) // 验证所有者的缓存被清除
 }