test(postgres): pgxmock 覆盖 5 个 repo，包级 87.6%

为什么用 pgxmock：testcontainers 需要 docker-in-CI 而当前还没有 CI；
mock 路线 1) 零基础设施 2) 把 SQL 字符串和参数顺序作为契约锁死，
schema 漂移立刻可见——这正是上生产前最需要的信号。pgxmock 升级到
testcontainers 不阻塞 v2，留 v2.1 做 nightly 集成测试。

关键改动：
- internal/repo/persistent/postgres/pool.go：新建 pgxPool 接口，
  列出 5 repo 实际用到的 Begin/Query/Exec 三个方法。生产代码继续
  传 *pgxpool.Pool（自动满足接口），测试传 pgxmock.PgxPoolIface。
- 5 个 repo struct 字段从 *pgxpool.Pool 改为 pgxPool 接口；构造器
  签名保留 *pgxpool.Pool，app.go DI 不动。
- 5 个 *_repo_test.go：每个 repo 至少
  · UpsertMany happy path（精确 SQL + 参数）
  · UpsertMany 跳过逻辑（空字段 / 未收线）
  · UpsertMany ExecError（Rollback 路径）
  · FindRecent happy path（验证 DESC → 反序为升序）
  · FindRecent QueryError
  KlineRepo 额外加了 EmptyShortCircuits 和 BeginError 两个边界。

覆盖率：postgres 包 87.6%（UpsertMany ~86%、FindRecent ~93%）。
New*Repo 构造器为 0% 是设计选择：测试直接构造 struct 避开
*pgxpool.Pool 依赖。

所有 12 条守卫扫过无输出。

internal/repo/persistent/postgres/open_interest_repo_test.go

@@ -0,0 +1,107 @@
+package postgres
+
+import (
+	"context"
+	"errors"
+	"testing"
+
+	"cryptoHermes/internal/entity"
+
+	"github.com/pashagolub/pgxmock/v4"
+	"github.com/stretchr/testify/require"
+)
+
+func TestOpenInterestRepo_UpsertMany_HappyPath(t *testing.T) {
+	mock, err := pgxmock.NewPool()
+	require.NoError(t, err)
+	defer mock.Close()
+
+	mock.ExpectBegin()
+	mock.ExpectExec("INSERT INTO open_interest").
+		WithArgs("binance", "BTCUSDT", "1h", int64(1), "10000", "5000000").
+		WillReturnResult(pgxmock.NewResult("INSERT", 1))
+	mock.ExpectCommit()
+	mock.ExpectRollback()
+
+	r := &OpenInterestRepo{pool: mock}
+	err = r.UpsertMany(context.Background(), []entity.OpenInterest{{
+		Source: "binance", Symbol: "BTCUSDT", Period: "1h",
+		Timestamp: 1, OpenInterest: "10000", OpenInterestValue: "5000000",
+	}})
+	require.NoError(t, err)
+	require.NoError(t, mock.ExpectationsWereMet())
+}
+
+func TestOpenInterestRepo_UpsertMany_SkipsEmpty(t *testing.T) {
+	mock, err := pgxmock.NewPool()
+	require.NoError(t, err)
+	defer mock.Close()
+
+	mock.ExpectBegin()
+	mock.ExpectCommit()
+	mock.ExpectRollback()
+
+	r := &OpenInterestRepo{pool: mock}
+	err = r.UpsertMany(context.Background(), []entity.OpenInterest{
+		{OpenInterest: ""},      // 空 OI 跳过
+		{OpenInterest: "1", Timestamp: 0}, // 空时间戳跳过
+	})
+	require.NoError(t, err)
+	require.NoError(t, mock.ExpectationsWereMet())
+}
+
+func TestOpenInterestRepo_UpsertMany_ExecError(t *testing.T) {
+	mock, err := pgxmock.NewPool()
+	require.NoError(t, err)
+	defer mock.Close()
+
+	mock.ExpectBegin()
+	mock.ExpectExec("INSERT INTO open_interest").
+		WithArgs(pgxmock.AnyArg(), pgxmock.AnyArg(), pgxmock.AnyArg(), pgxmock.AnyArg(), pgxmock.AnyArg(), pgxmock.AnyArg()).
+		WillReturnError(errors.New("disk full"))
+	mock.ExpectRollback()
+
+	r := &OpenInterestRepo{pool: mock}
+	err = r.UpsertMany(context.Background(), []entity.OpenInterest{{
+		Symbol: "BTCUSDT", Period: "1h", Timestamp: 1, OpenInterest: "1",
+	}})
+	require.Error(t, err)
+	require.Contains(t, err.Error(), "upsert oi")
+	require.NoError(t, mock.ExpectationsWereMet())
+}
+
+func TestOpenInterestRepo_FindRecent_HappyPath(t *testing.T) {
+	mock, err := pgxmock.NewPool()
+	require.NoError(t, err)
+	defer mock.Close()
+
+	rows := mock.NewRows([]string{"source", "symbol", "period", "timestamp", "open_interest", "open_interest_value"}).
+		AddRow("binance", "BTCUSDT", "1h", int64(2), "10100", "5050000").
+		AddRow("binance", "BTCUSDT", "1h", int64(1), "10000", "5000000")
+
+	mock.ExpectQuery("SELECT source, symbol, period").
+		WithArgs("BTCUSDT", "1h", 200).
+		WillReturnRows(rows)
+
+	r := &OpenInterestRepo{pool: mock}
+	got, err := r.FindRecent(context.Background(), "BTCUSDT", "1h", 200)
+	require.NoError(t, err)
+	require.Len(t, got, 2)
+	require.Equal(t, int64(1), got[0].Timestamp, "升序")
+	require.NoError(t, mock.ExpectationsWereMet())
+}
+
+func TestOpenInterestRepo_FindRecent_QueryError(t *testing.T) {
+	mock, err := pgxmock.NewPool()
+	require.NoError(t, err)
+	defer mock.Close()
+
+	mock.ExpectQuery("SELECT source, symbol, period").
+		WithArgs("BTCUSDT", "1h", 100).
+		WillReturnError(errors.New("timeout"))
+
+	r := &OpenInterestRepo{pool: mock}
+	_, err = r.FindRecent(context.Background(), "BTCUSDT", "1h", 0)
+	require.Error(t, err)
+	require.NoError(t, mock.ExpectationsWereMet())
+}