重构任务节点对话框和JS脚本选择窗口，调整命名空间，优化代码结构

BetterGenshinImpact/View/Windows/GearTask/AddTaskNodeDialog.xaml.cs

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+using System;
+using System.Windows;
+using BetterGenshinImpact.Helpers.Ui;
+using AddTaskNodeDialogViewModel = BetterGenshinImpact.ViewModel.Windows.GearTask.AddTaskNodeDialogViewModel;
+
+namespace BetterGenshinImpact.View.Windows.GearTask;
+
+public partial class AddTaskNodeDialog
+{
+    public AddTaskNodeDialogViewModel ViewModel { get; }
+
+    public AddTaskNodeDialog(string taskType)
+    {
+        ViewModel = new AddTaskNodeDialogViewModel(taskType);
+        DataContext = ViewModel;
+        
+        InitializeComponent();
+        
+        ViewModel.RequestClose += OnRequestClose;
+        this.SourceInitialized += OnSourceInitialized;
+    }
+
+    private void OnSourceInitialized(object? sender, EventArgs e)
+    {
+        // 应用与主窗口相同的背景主题
+        WindowHelper.TryApplySystemBackdrop(this);
+    }
+
+    private void OnRequestClose(object? sender, bool result)
+    {
+        DialogResult = result;
+        Close();
+    }
+
+    /// <summary>
+    /// 显示添加任务对话框
+    /// </summary>
+    /// <param name="taskType">任务类型</param>
+    /// <param name="owner">父窗口</param>
+    /// <returns>如果用户点击确定返回ViewModel，否则返回null</returns>
+    public static AddTaskNodeDialogViewModel? ShowDialog(string taskType, Window? owner = null)
+    {
+        var dialog = new AddTaskNodeDialog(taskType);
+        if (owner != null)
+        {
+            dialog.Owner = owner;
+        }
+        
+        var result = dialog.ShowDialog();
+        return result == true ? dialog.ViewModel : null;
+    }
+}