fix(wechat): 初始化定时任务运行状态

- 将 `isRunning` 属性默认值设置为 `false`
- 避免因未初始化导致的潜在运行异常

src/Cron/AccessTokenCron.php

@@ -24,7 +24,7 @@ class AccessTokenCron extends BaseJob
 
     private string $cacheKey;
 
-    private bool $isRunning;
+    private bool $isRunning = false;
 
     public function __construct(private MiniApp $miniApp)
     {