fix(queue): 防止过期执行占位阻塞与重复提交

队列恢复后，仍在运行标记中的 River job 可能保留 waiting admission，形成全局 FIFO 队头阻塞；同时旧执行在租约被接管后仍可能创建 attempt 或切换到 submitting。

新增 stale admission 自动让出机制，并用当前 execution token 对 attempt 创建和上游提交状态切换做 fencing。任务、River job 和结算状态均不在让出流程中改写。

验证：go vet ./...；env -u AI_GATEWAY_TEST_DATABASE_URL go test ./... -count=1；真实 PostgreSQL 集成测试覆盖 stale admission 让出与旧 token 提交拦截。

apps/api/internal/store/billing_v2_integration_test.go

@@ -48,6 +48,15 @@ func TestTaskIdempotencyAndExecutionLease(t *testing.T) {
 	if err := db.RenewTaskExecutionLease(ctx, created.Task.ID, firstToken, 5*time.Minute); err != nil {
 		t.Fatalf("renew first lease: %v", err)
 	}
+	firstAttemptID, err := db.CreateTaskAttempt(ctx, CreateTaskAttemptInput{
+		TaskID:         created.Task.ID,
+		ExecutionToken: firstToken,
+		AttemptNo:      1,
+		Status:         "running",
+	})
+	if err != nil {
+		t.Fatalf("create first owned attempt: %v", err)
+	}
 	if _, err := db.pool.Exec(ctx, `UPDATE gateway_tasks SET execution_lease_expires_at=now()-interval '1 second' WHERE id=$1::uuid`, created.Task.ID); err != nil {
 		t.Fatal(err)
 	}
@@ -55,6 +64,41 @@ func TestTaskIdempotencyAndExecutionLease(t *testing.T) {
 	if _, err := db.ClaimTaskExecution(ctx, created.Task.ID, secondToken, 5*time.Minute); err != nil {
 		t.Fatalf("take over expired lease: %v", err)
 	}
+	if err := db.SetAttemptUpstreamSubmissionStatusForExecution(
+		ctx,
+		firstAttemptID,
+		created.Task.ID,
+		firstToken,
+		"submitting",
+	); !errors.Is(err, ErrTaskExecutionLeaseLost) {
+		t.Fatalf("stale attempt submission fence error=%v", err)
+	}
+	if _, err := db.CreateTaskAttempt(ctx, CreateTaskAttemptInput{
+		TaskID:         created.Task.ID,
+		ExecutionToken: firstToken,
+		AttemptNo:      2,
+		Status:         "running",
+	}); !errors.Is(err, ErrTaskExecutionLeaseLost) {
+		t.Fatalf("stale attempt creation fence error=%v", err)
+	}
+	secondAttemptID, err := db.CreateTaskAttempt(ctx, CreateTaskAttemptInput{
+		TaskID:         created.Task.ID,
+		ExecutionToken: secondToken,
+		AttemptNo:      2,
+		Status:         "running",
+	})
+	if err != nil {
+		t.Fatalf("create current owned attempt: %v", err)
+	}
+	if err := db.SetAttemptUpstreamSubmissionStatusForExecution(
+		ctx,
+		secondAttemptID,
+		created.Task.ID,
+		secondToken,
+		"submitting",
+	); err != nil {
+		t.Fatalf("current attempt submission fence: %v", err)
+	}
 	if _, err := db.FinishTaskFailure(ctx, FinishTaskFailureInput{TaskID: created.Task.ID, ExecutionToken: firstToken, Code: "old_worker", Message: "old"}); !errors.Is(err, ErrTaskExecutionLeaseLost) {
 		t.Fatalf("old worker terminal error=%v", err)
 	}