refactor: 插件窗体由 static 单例状态改为实例字段（对齐 TextViewer）

将 10 个 CycleGUI 窗体/管理器从进程级 static 单例状态改为实例字段 + 实例方法，
消除本地端/Web 端共享同一可变状态的隐患（对齐 TextViewer 正例）。

每个类保留一个 private static _instance 单实例持有者；静态入口 Open()/OpenViewer()
与实例 Show() 均转发到该实例，调用方零改动、单实例“置前”行为不变。

涉及：ChargeStationManagementForm、ChargeStrategyConfigForm、CommunicationMonitorForm、
AlarmConfigManagementForm、ButtonBoxManager、DoorManager、DoorMonitor、
LoopViewer、DeliveryViewer、TrafficInterlockViewer。

构建：dotnet build StandardScene.sln --no-incremental → 0 错误，30 警告（与基线一致，无新增）。

StandardScene.Core/Chained/DeliveryViewer.cs

@@ -28,26 +28,30 @@ namespace StandardScene.Chained
         private const int OverdueMinutesThreshold = 10000; // 约 7 天视为超时
         private const string TableId = "delivery-task-list";
 
-        private static readonly HttpClient SharedHttpClient = new HttpClient();
+        private readonly HttpClient SharedHttpClient = new HttpClient();
         /// <summary>超时任务整行底色（深色主题下的暗红，醒目但不刺眼）。</summary>
-        private static readonly Color OverdueRowColor = Color.FromArgb(255, 90, 36, 36);
+        private readonly Color OverdueRowColor = Color.FromArgb(255, 90, 36, 36);
 
-        private static Panel _panel;
-        private static bool _showFinished = true;   // 显示已完成任务
-        private static bool _showAbolished = true;  // 显示废止任务（Error / Canceled / Terminated）
+        private Panel _panel;
+        private bool _showFinished = true;   // 显示已完成任务
+        private bool _showAbolished = true;  // 显示废止任务（Error / Canceled / Terminated）
 
         // 渲染快照：由后台线程按 FlushInterval 刷新，渲染线程只读引用；锁/文件 IO 绝不放在渲染线程，避免界面卡死。
-        private static volatile List<Delivery> _snapshot = new List<Delivery>();
-        private static volatile bool _refreshing;
-        private static DateTime _lastFlush = DateTime.MinValue;
-        private static readonly TimeSpan FlushInterval = TimeSpan.FromSeconds(1);
-        private static volatile string _status = "";
+        private volatile List<Delivery> _snapshot = new List<Delivery>();
+        private volatile bool _refreshing;
+        private DateTime _lastFlush = DateTime.MinValue;
+        private readonly TimeSpan FlushInterval = TimeSpan.FromSeconds(1);
+        private volatile string _status = "";
 
         /// <summary>打开（或置前）任务管理面板。兼容原 <c>new DeliveryViewer().Show()</c> 调用方式。</summary>
         public void Show() => Open();
 
         /// <summary>打开（或置前）任务管理面板。</summary>
-        public static void Open()
+        public static void Open() => (_instance ??= new DeliveryViewer()).OpenCore();
+
+        private static DeliveryViewer _instance;
+
+        private void OpenCore()
         {
             if (_panel != null)
             {
@@ -127,14 +131,14 @@ namespace StandardScene.Chained
             });
         }
 
-        private static bool IsOverdue(Delivery dd) =>
+        private bool IsOverdue(Delivery dd) =>
             (DateTime.Now - dd.CreateTime).TotalMinutes > OverdueMinutesThreshold;
 
         /// <summary>
         /// 渲染线程调用：到达刷新间隔且无在途刷新时，<b>在后台线程</b>重新拉取任务快照（超时任务置顶）。
         /// 业务侧的锁与文件 IO 一律放到后台，渲染线程只读 <see cref="_snapshot"/> 引用，避免界面卡死。
         /// </summary>
-        private static void EnsureSnapshotFresh()
+        private void EnsureSnapshotFresh()
         {
             if (_refreshing) return;
             if (DateTime.Now - _lastFlush < FlushInterval) return;
@@ -165,14 +169,14 @@ namespace StandardScene.Chained
             });
         }
 
-        private static string SafeSiteName(int siteId)
+        private string SafeSiteName(int siteId)
         {
             try { return SimpleLib.GetSite(siteId)?.name ?? ""; }
             catch { return ""; }
         }
 
         /// <summary>将任务标记为已取消（Canceled）。</summary>
-        private static void MarkDeliveryCanceled(Delivery d)
+        private void MarkDeliveryCanceled(Delivery d)
         {
             if (d == null) return;
             lock (d.SyncStatus)
@@ -187,7 +191,7 @@ namespace StandardScene.Chained
         /// 当 clearCarForChange=true 时，仅当状态为 Suspended 或 Waiting 且未处于放货阶段时，
         /// 才会清空 UsingCar 并返回 true；否则返回 false。
         /// </summary>
-        private static bool MarkDeliveryWaiting(Delivery d, bool clearCarForChange)
+        private bool MarkDeliveryWaiting(Delivery d, bool clearCarForChange)
         {
             if (d == null) return false;
             lock (d.SyncStatus)
@@ -217,7 +221,7 @@ namespace StandardScene.Chained
             }
         }
 
-        private static void ResendDelivery(string taskCode)
+        private void ResendDelivery(string taskCode)
         {
             try
             {
@@ -247,7 +251,7 @@ namespace StandardScene.Chained
             }
         }
 
-        private static void CancelDelivery(string taskCode)
+        private void CancelDelivery(string taskCode)
         {
             try
             {
@@ -286,7 +290,7 @@ namespace StandardScene.Chained
             }
         }
 
-        private static void ChangeCarResendDelivery(string taskCode)
+        private void ChangeCarResendDelivery(string taskCode)
         {
             try
             {