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/Charge/ChargeStrategyConfigForm.cs

@@ -9,39 +9,43 @@ namespace StandardScene.Charge
     /// </summary>
     public class ChargeStrategyConfigForm
     {
-        private static Panel _panel;
-        private static readonly ChargeStrategyConfigService ConfigService = ChargeStrategyConfigService.Instance;
+        private Panel _panel;
+        private readonly ChargeStrategyConfigService ConfigService = ChargeStrategyConfigService.Instance;
 
-        private static ChargeStrategyConfig _config;
-        private static string _status = "";
+        private ChargeStrategyConfig _config;
+        private string _status = "";
 
         // SOC 参数
-        private static float _mustChargeSoc;
-        private static float _idleChargeSoc;
-        private static float _taskAvailableSoc;
-        private static float _fullChargeSoc;
-        private static float _allowInterruptSoc;
+        private float _mustChargeSoc;
+        private float _idleChargeSoc;
+        private float _taskAvailableSoc;
+        private float _fullChargeSoc;
+        private float _allowInterruptSoc;
 
         // 时间参数
-        private static float _idleChargeSeconds;
-        private static float _idleSeconds;
-        private static float _mustChargeSeconds;
-        private static float _topUpMinutes;
+        private float _idleChargeSeconds;
+        private float _idleSeconds;
+        private float _mustChargeSeconds;
+        private float _topUpMinutes;
 
         // 任务参数
-        private static int _minAllowFreeCarToChargeTaskCnt;
+        private int _minAllowFreeCarToChargeTaskCnt;
 
         // 开关参数
-        private static bool _allowInterruptTask;
-        private static bool _useLowerSocForCharge;
-        private static bool _enableErrorChargeDetection;
-        private static bool _useChargeSiteFilter;
+        private bool _allowInterruptTask;
+        private bool _useLowerSocForCharge;
+        private bool _enableErrorChargeDetection;
+        private bool _useChargeSiteFilter;
 
         /// <summary>打开（或置前）充电策略配置面板。兼容原 <c>new ChargeStrategyConfigForm().Show()</c> 调用方式。</summary>
         public void Show() => Open();
 
         /// <summary>打开（或置前）充电策略配置面板。</summary>
-        public static void Open()
+        public static void Open() => (_instance ??= new ChargeStrategyConfigForm()).OpenCore();
+
+        private static ChargeStrategyConfigForm _instance;
+
+        private void OpenCore()
         {
             if (_panel != null)
             {
@@ -120,7 +124,7 @@ namespace StandardScene.Charge
             });
         }
 
-        private static bool TryLoadConfig()
+        private bool TryLoadConfig()
         {
             try
             {
@@ -137,7 +141,7 @@ namespace StandardScene.Charge
             }
         }
 
-        private static void ApplyConfigToUi(ChargeStrategyConfig config)
+        private void ApplyConfigToUi(ChargeStrategyConfig config)
         {
             _mustChargeSoc = (float)config.MustChargeSoc;
             _idleChargeSoc = (float)config.IdleChargeSoc;
@@ -158,7 +162,7 @@ namespace StandardScene.Charge
             _useChargeSiteFilter = config.UseChargeSiteFilter;
         }
 
-        private static void ApplyUiToConfig()
+        private void ApplyUiToConfig()
         {
             _config.MustChargeSoc = _mustChargeSoc;
             _config.IdleChargeSoc = _idleChargeSoc;
@@ -180,7 +184,7 @@ namespace StandardScene.Charge
         }
 
         /// <summary>验证 SOC 阈值之间的逻辑关系（保存前）。</summary>
-        private static bool ValidateSocRanges(out string errorMessage)
+        private bool ValidateSocRanges(out string errorMessage)
         {
             if (_mustChargeSoc >= _idleChargeSoc)
             {
@@ -210,7 +214,7 @@ namespace StandardScene.Charge
             return true;
         }
 
-        private static void TrySave(bool closeAfterSave)
+        private void TrySave(bool closeAfterSave)
         {
             ApplyUiToConfig();
 
@@ -245,7 +249,7 @@ namespace StandardScene.Charge
             }
         }
 
-        private static void RestoreDefaults()
+        private void RestoreDefaults()
         {
             CycleUiHelper.ConfirmThen("确定要恢复默认配置吗？当前配置将被覆盖。", () =>
             {