feat: 管理器支持深浅主题切换，发布 exe

- 新增 LightTheme.xaml 浅色主题资源
- 标题栏添加主题切换按钮（☀️/🌙）
- Manager 支持深浅主题互换
- 发布 Manager.exe (292KB) 和 Installer.exe (171KB)
- 插件安装包 Better-Seewo.2.0.0.exe (11.6MB)

Manager/MainWindow.xaml.cs

@@ -1,3 +1,4 @@
+using System;
 using System.Windows;
 using System.Windows.Controls;
 
@@ -5,18 +6,42 @@ namespace BetterSeewoManager;
 
 public partial class MainWindow : Window
 {
+    private bool _isDarkTheme = true;
+
     public MainWindow()
     {
         InitializeComponent();
-        ContentFrame.Navigate(new System.Uri("Pages/InstallPage.xaml", System.UriKind.Relative));
+        ApplyTheme();
+        ContentFrame.Navigate(new Uri("Pages/InstallPage.xaml", UriKind.Relative));
     }
 
     private void Tab_Click(object sender, RoutedEventArgs e)
     {
         if (sender is RadioButton rb && rb.Tag is string pageName)
         {
-            var pageUri = new System.Uri($"Pages/{pageName}.xaml", System.UriKind.Relative);
+            var pageUri = new Uri($"Pages/{pageName}.xaml", UriKind.Relative);
             ContentFrame.Navigate(pageUri);
         }
     }
+
+    private void BtnThemeToggle_Click(object sender, RoutedEventArgs e)
+    {
+        _isDarkTheme = !_isDarkTheme;
+        ApplyTheme();
+    }
+
+    private void ApplyTheme()
+    {
+        var app = (App)Application.Current;
+        app.Resources.MergedDictionaries.Clear();
+        app.Resources.MergedDictionaries.Add(new ResourceDictionary
+        {
+            Source = new Uri(_isDarkTheme
+                ? "Themes/DarkTheme.xaml"
+                : "Themes/LightTheme.xaml", UriKind.Relative)
+        });
+
+        BtnThemeToggle.Content = _isDarkTheme ? "☀️" : "🌙";
+        StatusText.Text = _isDarkTheme ? "已切换到深色主题" : "已切换到浅色主题";
+    }
 }