feat(交易信号): 持仓状态持久化至 Redis 以保障重启与多实例下均价计算准确

Motivation:
持仓与已处理信号的状态此前仅存于进程内存，服务重启或多实例部署后会丢失，导致加仓均价、仓位大小等计算失真，重复信号也无法跨实例幂等。通过将状态持久化到 Redis，保证持仓跟踪跨重启、跨实例连续一致，提升通知内容的准确性与可靠性。

Changes:

* 新增持仓存储抽象，支持内存与 Redis 两种实现，持仓状态与已处理信号快照按 TTL 持久化
* 持仓变更通过 Redis 事务管道原子提交，保证状态更新与幂等记录一致写入
* 存储写入失败时消息进入重试而非直接确认，避免状态丢失导致通知失真
* 缓存层新增原始值读取与批量事务写入能力，并在订阅器初始化时注入 Redis 依赖
* 补充跨实例持久化、幂等去重与存储失败场景的测试覆盖

internal/subscriber/tradesignal/store_test.go

@@ -0,0 +1,117 @@
+package tradesignal
+
+import (
+	"context"
+	"errors"
+	"math"
+	"sync"
+	"testing"
+
+	"aiaa-notification-service/internal/cache"
+)
+
+type fakeKV struct {
+	mu   sync.Mutex
+	data map[string][]byte
+	fail bool
+}
+
+func newFakeKV() *fakeKV {
+	return &fakeKV{data: make(map[string][]byte)}
+}
+
+func (f *fakeKV) GetRaw(_ context.Context, key string) ([]byte, error) {
+	if f.fail {
+		return nil, errors.New("redis down")
+	}
+	f.mu.Lock()
+	defer f.mu.Unlock()
+	if b, ok := f.data[key]; ok {
+		return append([]byte(nil), b...), nil
+	}
+	return nil, nil
+}
+
+func (f *fakeKV) TxWrite(_ context.Context, writes []cache.KVWrite) error {
+	if f.fail {
+		return errors.New("redis down")
+	}
+	f.mu.Lock()
+	defer f.mu.Unlock()
+	for _, w := range writes {
+		if w.Delete {
+			delete(f.data, w.Key)
+			continue
+		}
+		f.data[w.Key] = append([]byte(nil), w.Val...)
+	}
+	return nil
+}
+
+func TestTrackerPersistsAcrossMemoryInstances(t *testing.T) {
+	store := newMemoryStore()
+	mustApply(t, NewTrackerWithStore(store), &Signal{
+		SignalID: "p1", StrategyCode: "BLONG", Symbol: "PEPEUSDT", Side: "SHORT",
+		Action: "OPEN", Quantity: ptr(10), Price: 0.00000059,
+	})
+	snap := mustApply(t, NewTrackerWithStore(store), &Signal{
+		SignalID: "p2", StrategyCode: "BLONG", Symbol: "PEPEUSDT", Side: "SHORT",
+		Action: "ADD", Quantity: ptr(10), Price: 0.00000061,
+	})
+	if math.Abs(snap.AvgPrice-0.0000006) > 1e-12 {
+		t.Fatalf("shared memory store avg=%v", snap.AvgPrice)
+	}
+}
+
+func TestTrackerPersistsAcrossRedisInstances(t *testing.T) {
+	store := &redisStore{c: newFakeKV()}
+	mustApply(t, NewTrackerWithStore(store), &Signal{
+		SignalID: "r1", StrategyCode: "BLONG", Symbol: "PEPEUSDT", Side: "SHORT",
+		Action: "OPEN", Quantity: ptr(10), Price: 100,
+	})
+	snap := mustApply(t, NewTrackerWithStore(store), &Signal{
+		SignalID: "r2", StrategyCode: "BLONG", Symbol: "PEPEUSDT", Side: "SHORT",
+		Action: "ADD", Quantity: ptr(10), Price: 200,
+	})
+	if math.Abs(snap.AvgPrice-150) > 1e-9 {
+		t.Fatalf("shared redis store avg=%v", snap.AvgPrice)
+	}
+}
+
+func TestTrackerRedisIdempotentAcrossInstances(t *testing.T) {
+	store := &redisStore{c: newFakeKV()}
+	open := &Signal{
+		SignalID: "same", StrategyCode: "BLONG", Symbol: "BTCUSDT", Side: "LONG",
+		Action: "OPEN", Quantity: ptr(1), Price: 100,
+	}
+	mustApply(t, NewTrackerWithStore(store), open)
+	mustApply(t, NewTrackerWithStore(store), open)
+	snap := mustApply(t, NewTrackerWithStore(store), &Signal{
+		SignalID: "add", StrategyCode: "BLONG", Symbol: "BTCUSDT", Side: "LONG",
+		Action: "ADD", Quantity: ptr(1), Price: 200,
+	})
+	if math.Abs(snap.AvgPrice-150) > 1e-9 {
+		t.Fatalf("replayed open should not double size, avg=%v", snap.AvgPrice)
+	}
+}
+
+func TestTrackerRedisStoreError(t *testing.T) {
+	tr := NewTrackerWithStore(&redisStore{c: &fakeKV{fail: true, data: map[string][]byte{}}})
+	_, err := tr.Apply(&Signal{
+		SignalID: "e1", StrategyCode: "BLONG", Symbol: "BTCUSDT", Side: "LONG",
+		Action: "OPEN", Quantity: ptr(1), Price: 100,
+	})
+	if err == nil {
+		t.Fatal("expected store error")
+	}
+}
+
+func TestConvertPositionStoreError(t *testing.T) {
+	c := &Converter{
+		positions: NewTrackerWithStore(&redisStore{c: &fakeKV{fail: true, data: map[string][]byte{}}}),
+	}
+	_, _, err := c.Convert([]byte(`{"action":"OPEN","symbol":"BTCUSDT","price":1,"quantity":1}`))
+	if !errors.Is(err, ErrPositionStore) {
+		t.Fatalf("err=%v", err)
+	}
+}