添加单实例限制、应用图标、移除托盘设置菜单、快捷键暂停/恢复功能

单实例限制：通过命名Mutex和窗口消息广播确保只能运行一个实例，再次启动时唤起已有窗口

应用图标：exe文件嵌入app.ico，托盘和窗口图标统一使用该图标文件

移除托盘右键菜单中与显示主界面重复的设置选项

快捷键暂停/恢复：托盘菜单和主界面侧边栏均添加切换按钮，通过MainViewModel.IsHotKeyEnabled双向同步

PersonalToolBox/Views/MainWindow.xaml

@@ -178,6 +178,7 @@
                         <RowDefinition Height="42"/>
                         <RowDefinition Height="42"/>
                         <RowDefinition Height="45"/>
+                        <RowDefinition Height="45"/>
                     </Grid.RowDefinitions>
 
                     <ListBox Grid.Row="0"
@@ -277,7 +278,7 @@
                             BorderBrush="{DynamicResource Theme.CardBorder}"
                             Foreground="{DynamicResource Theme.Foreground}"
                             FontSize="12"
-                            Height="35" Margin="10,0,10,10"
+                            Height="35" Margin="10,0,10,3"
                             Cursor="Hand">
                         <StackPanel Orientation="Horizontal">
                             <TextBlock Text="◐" FontSize="16" Margin="0,0,8,0"
@@ -285,6 +286,28 @@
                             <TextBlock Text="切换主题" VerticalAlignment="Center"/>
                         </StackPanel>
                     </Button>
+
+                    <Button Grid.Row="4"
+                            Command="{Binding ToggleHotKeyCommand}"
+                            Background="Transparent"
+                            BorderThickness="1"
+                            BorderBrush="{DynamicResource Theme.CardBorder}"
+                            Foreground="{DynamicResource Theme.Foreground}"
+                            FontSize="12"
+                            Height="35" Margin="10,0,10,10"
+                            Cursor="Hand">
+                        <Button.Resources>
+                            <Style TargetType="TextBlock">
+                                <Setter Property="Text" Value="⏸ 暂停快捷键"/>
+                                <Style.Triggers>
+                                    <DataTrigger Binding="{Binding IsHotKeyEnabled}" Value="False">
+                                        <Setter Property="Text" Value="▶ 恢复快捷键"/>
+                                    </DataTrigger>
+                                </Style.Triggers>
+                            </Style>
+                        </Button.Resources>
+                        <TextBlock VerticalAlignment="Center" TextAlignment="Center"/>
+                    </Button>
                 </Grid>
             </Border>