Add OOBE redesign, theme & data location support

Introduce a redesigned OOBE flow and data-location/theme support across the launcher. Adds a new ThemeService for applying light/dark and accent colors; integrates FluentIcons.Avalonia package for icons. Overhauls OobeWindow (UX animations, typing effect, multi-step theme and data-location pages, Monet options, and final welcome step) and its code-behind to handle step navigation, accent selection, and data-location resolution. Adds DataLocation UI and handlers (DataLocationPromptWindow changes, DataLocation resolver usage) and wires a DevDebug UI for toggling/opening the data-location page. UpdateEngineService now resolves the launcher root via DataLocationResolver. Misc: update various view models, localization entries and remove TrimmerRoots.xml.

LanMountainDesktop.Launcher/Services/ThemeService.cs

@@ -0,0 +1,68 @@
+using Avalonia;
+using Avalonia.Styling;
+using FluentAvalonia.Styling;
+
+namespace LanMountainDesktop.Launcher.Services;
+
+/// <summary>
+/// 主题服务，管理启动器的主题设置
+/// </summary>
+public static class ThemeService
+{
+    private static ThemeVariant _currentTheme = ThemeVariant.Light;
+    private static string _accentColor = "#0078D4";
+
+    /// <summary>
+    /// 获取当前主题
+    /// </summary>
+    public static ThemeVariant CurrentTheme => _currentTheme;
+
+    /// <summary>
+    /// 获取当前主题色
+    /// </summary>
+    public static string AccentColor => _accentColor;
+
+    /// <summary>
+    /// 应用主题设置
+    /// </summary>
+    public static void ApplyTheme(ThemeMode mode, string accentColor)
+    {
+        _currentTheme = mode switch
+        {
+            ThemeMode.Dark => ThemeVariant.Dark,
+            _ => ThemeVariant.Light
+        };
+        _accentColor = accentColor;
+
+        // 应用到当前应用程序
+        if (Application.Current is { } app)
+        {
+            app.RequestedThemeVariant = _currentTheme;
+        }
+    }
+
+    /// <summary>
+    /// 应用浅色主题
+    /// </summary>
+    public static void ApplyLightTheme(string accentColor)
+    {
+        ApplyTheme(ThemeMode.Light, accentColor);
+    }
+
+    /// <summary>
+    /// 应用深色主题
+    /// </summary>
+    public static void ApplyDarkTheme(string accentColor)
+    {
+        ApplyTheme(ThemeMode.Dark, accentColor);
+    }
+}
+
+/// <summary>
+/// 主题模式
+/// </summary>
+public enum ThemeMode
+{
+    Light,
+    Dark
+}

LanMountainDesktop.Launcher/Services/UpdateEngineService.cs

@@ -22,6 +22,7 @@ internal sealed class UpdateEngineService
 
     private readonly DeploymentLocator _deploymentLocator;
     private readonly string _appRoot;
+    private readonly string _dataRoot;
     private readonly string _launcherRoot;
     private readonly string _incomingRoot;
     private readonly string _snapshotsRoot;
@@ -30,7 +31,8 @@ internal sealed class UpdateEngineService
     {
         _deploymentLocator = deploymentLocator;
         _appRoot = deploymentLocator.GetAppRoot();
-        _launcherRoot = Path.Combine(_appRoot, LauncherDirectoryName);
+        _dataRoot = new DataLocationResolver(_appRoot).ResolveDataRoot();
+        _launcherRoot = Path.Combine(_dataRoot, LauncherDirectoryName);
         _incomingRoot = Path.Combine(_launcherRoot, UpdateDirectoryName, IncomingDirectoryName);
         _snapshotsRoot = Path.Combine(_launcherRoot, SnapshotsDirectoryName);
     }