perf(worker): 消除运行态计数跨城热行阻塞

将仅用于候选负载均衡的 runtime_client_states 分配和释放写入改为事务级异步提交，避免同步复制期间持续持有单候选热行锁。\n\n运行态计数仍由本地 WAL 持久化，并在运行时恢复中按 running attempt 重建；任务、账务、租约和状态提交不受影响。新增 PostgreSQL 并发与恢复集成测试。\n\n验证：go vet ./...；go test ./... -count=1；64 并发 PostgreSQL 集成测试；迁移安全检查；gofmt；git diff --check。

apps/api/internal/store/rate_limits.go

@@ -717,6 +717,23 @@ WHERE admission.task_id = task.id
 		return RuntimeRecoveryResult{}, err
 	}
 	result.CleanedTaskAdmissions += tag.RowsAffected()
+	if _, err := tx.Exec(ctx, `
+UPDATE runtime_client_states state
+SET running_count = (
+      SELECT count(*)
+      FROM gateway_task_attempts attempt
+      WHERE attempt.client_id = state.client_id
+        AND attempt.status = 'running'
+    ),
+    updated_at = now()
+WHERE state.running_count IS DISTINCT FROM (
+  SELECT count(*)
+  FROM gateway_task_attempts attempt
+  WHERE attempt.client_id = state.client_id
+    AND attempt.status = 'running'
+)`); err != nil {
+		return RuntimeRecoveryResult{}, err
+	}
 
 	return result, tx.Commit(ctx)
 }