refactor(link): bound every teardown and handler wait behind one helper [CI]

backend/fleet/src/Fleet.Server.Abstractions/FleetServerOptions.cs

@@ -16,6 +16,9 @@ public sealed class FleetServerOptions
 
     public TimeSpan RequestTimeout { get; set; } = TimeSpan.FromSeconds(15);
 
+    /// <summary>处理节点的一条消息（心跳、hello、收件箱）最多用这么久：钩子卡在数据库或外部查询里时，不能让这条连接停在「在线」而收不到任何心跳超时。超过就断开，节点按退避重连。</summary>
+    public TimeSpan HandlerTimeout { get; set; } = TimeSpan.FromSeconds(30);
+
     /// <summary>节点违反协议（方法没有声明、方向、类型或角色不对）的次数上限；超过就断开这条连接。</summary>
     public int MaxViolations { get; set; } = 20;
 }