fix(仓储): 修复查询关闭错误并迁移集成测试

修复 rows.Close 失败时的错误返回逻辑
迁移网关路由集成测试到 ent 事务基建
补齐仓储接口变更对应的测试桩方法
新增 backend/Makefile 统一测试命令
测试: GOTOOLCHAIN=go1.24.11 go test ./...
测试: golangci-lint run ./... --timeout=5m
测试: make test-integration

backend/internal/service/gemini_multiplatform_test.go

@@ -25,6 +25,14 @@ func (m *mockAccountRepoForGemini) GetByID(ctx context.Context, id int64) (*Acco
 	return nil, errors.New("account not found")
 }
 
+func (m *mockAccountRepoForGemini) ExistsByID(ctx context.Context, id int64) (bool, error) {
+	if m.accountsByID == nil {
+		return false, nil
+	}
+	_, ok := m.accountsByID[id]
+	return ok, nil
+}
+
 func (m *mockAccountRepoForGemini) ListSchedulableByPlatform(ctx context.Context, platform string) ([]Account, error) {
 	var result []Account
 	for _, acc := range m.accounts {