refactor：将DataLoaderService中的LoadAll*Async方法移到对应的管理服务中

- 将LoadAllDevicesAsync方法移到DeviceManagementService
 - 将LoadAllVariableTablesAsync方法移到VariableTableManagementService
 - 将LoadAllVariablesAsync方法移到VariableManagementService
 - 将LoadAllMenusAsync方法移到MenuManagementService
 - 将LoadAllMqttServersAsync方法移到MqttManagementService
 - 将LoadAllNlogsAsync方法移到LogManagementService
 - 更新DataLoaderService以使用管理服务提供的方法
 - 修改IDataLoaderService接口以移除这些方法
 - 保持与LoadAllTriggersAsync相同的模式
 - 遵循单一职责原则，提高代码一致性" (提交修改并添加描述性的提交信息)

DMS.Application/Services/Management/VariableManagementService.cs

@@ -275,4 +275,26 @@ public class VariableManagementService : IVariableManagementService
     }
 
     
+    /// <summary>
+    /// 异步加载所有变量数据到内存中。
+    /// </summary>
+    public async Task LoadAllVariablesAsync()
+    {
+        _appStorageService.Variables.Clear();
+
+        var variables = await _variableAppService.GetAllVariablesAsync();
+        // 将变量添加到安全字典
+        foreach (var variable in variables)
+        {
+            if (_appStorageService.VariableTables.TryGetValue(variable.VariableTableId,
+                                                                  out var variableTable))
+            {
+                variable.VariableTable = variableTable;
+                variableTable.Variables.Add(variable);
+            }
+
+            _appStorageService.Variables.TryAdd(variable.Id, variable);
+        }
+    }
+
 }