feat(bus): JetStream 流/KV 副本数可配(NATS_STREAM_REPLICAS,默认1)

三机/单机多节点集群部署需 Replicas=3,durable 流才有 Raft quorum 容错(计费/状态/
用量/评测/审批/入库回写不因单节点挂掉而丢)。此前 6 处 CreateOrUpdateStream + 1 处
KV 桶都未设 Replicas(默认1),集群等于白搭。加 streamReplicas() 读 env(合法值 1/3/5),
7 处统一带上。默认 1 保证单机/CI 不变。

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

sundynix-shared/bus/bus.go

@@ -113,6 +113,7 @@ func (b *Bus) EnsureTaskStream(ctx context.Context) error {
 		Name:     contract.StreamTasks,
 		Subjects: []string{contract.SubjectTasksAll},
 		Storage:  jetstream.FileStorage,
+		Replicas: streamReplicas(),
 	})
 	return err
 }
@@ -341,6 +342,7 @@ func (b *Bus) EnsureStatusStream(ctx context.Context) error {
 		Name:     contract.StreamStatus,
 		Subjects: []string{contract.SubjectTaskStatus},
 		Storage:  jetstream.FileStorage,
+		Replicas: streamReplicas(),
 		MaxAge:   24 * time.Hour, // 状态一天内必被消费，过期回收防无限增长
 	})
 	return err
@@ -399,6 +401,7 @@ func (b *Bus) EnsureEvalStream(ctx context.Context) error {
 		Name:     contract.StreamEval,
 		Subjects: []string{contract.SubjectEval},
 		Storage:  jetstream.FileStorage,
+		Replicas: streamReplicas(),
 		MaxAge:   24 * time.Hour, // 评测一天内必被消费，过期回收防无限增长
 	})
 	return err
@@ -453,6 +456,7 @@ func (b *Bus) EnsureUsageStream(ctx context.Context) error {
 		Name:     contract.StreamUsage,
 		Subjects: []string{contract.SubjectUsage},
 		Storage:  jetstream.FileStorage,
+		Replicas: streamReplicas(),
 		MaxAge:   72 * time.Hour, // 计费留足追赶窗口（网关长时间离线后仍能补齐）
 	})
 	return err
@@ -520,6 +524,7 @@ func (b *Bus) EnsureApprovalStream(ctx context.Context) error {
 		Name:     contract.StreamApprovals,
 		Subjects: []string{contract.SubjectApprovalAll},
 		Storage:  jetstream.FileStorage,
+		Replicas: streamReplicas(),
 		MaxAge:   24 * time.Hour,
 	})
 	return err
@@ -774,6 +779,18 @@ func DrainTimeout() time.Duration {
 	return 30 * time.Second
 }
 
+// streamReplicas 是 JetStream 流/KV 桶的副本数，经 NATS_STREAM_REPLICAS 配置，缺省 1。
+// 单机（单节点 NATS）保持 1；三机/单机多节点集群部署设 3，durable 流才有 Raft quorum 容错
+// （计费/状态/用量/评测/审批/入库回写不会因单节点挂掉而丢）。合法值 1/3/5（Raft 需奇数）。
+func streamReplicas() int {
+	if v := os.Getenv("NATS_STREAM_REPLICAS"); v != "" {
+		if n, err := strconv.Atoi(v); err == nil && (n == 1 || n == 3 || n == 5) {
+			return n
+		}
+	}
+	return 1
+}
+
 // drainWait 停止接新活后，等待在途 WaitGroup 跑完，或 dctx 到期放弃。
 func drainWait(wg *sync.WaitGroup, dctx context.Context) {
 	done := make(chan struct{})
@@ -890,6 +907,7 @@ func (b *Bus) EnsureIngestStream(ctx context.Context) error {
 		Name:     contract.StreamIngest,
 		Subjects: []string{contract.SubjectIngestAll},
 		Storage:  jetstream.FileStorage,
+		Replicas: streamReplicas(),
 		MaxAge:   ingestStreamMaxAge,
 	})
 	return err
@@ -1004,6 +1022,7 @@ func (b *Bus) Checkpoints(ctx context.Context, bucket string, ttl time.Duration)
 	kv, err := b.js.CreateOrUpdateKeyValue(ctx, jetstream.KeyValueConfig{
 		Bucket:   bucket,
 		Storage:  jetstream.FileStorage,
+		Replicas: streamReplicas(),
 		TTL:      ttl,
 	})
 	if err != nil {