Initial commit: FluidExplorer：从零实现的 WinUI 3 文件资源管理器替代品（Mica、命令栏、面包屑）

Services/AppServices.cs

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+using FluidExplorer.Services.FileSystem;
+using FluidExplorer.Services.Icons;
+using FluidExplorer.Services.Operations;
+using FluidExplorer.Services.Search;
+using FluidExplorer.ViewModels;
+using Microsoft.UI.Dispatching;
+
+namespace FluidExplorer.Services;
+
+/// <summary>组合根：所有服务在这里创建、装配，并交给视图模型。</summary>
+public sealed class AppServices
+{
+    public AppServices(DispatcherQueue ui)
+    {
+        Ui = ui;
+        Settings = AppSettings.Load();
+        FileSystem = new FastFileSystemService();
+        Search = new SearchService(FileSystem);
+        Icons = CreateIconService(ui);
+        Operations = CreateOperationService();
+        Main = new MainViewModel(FileSystem, Search, Operations, Icons, Settings, ui);
+    }
+
+    public DispatcherQueue Ui { get; }
+    public AppSettings Settings { get; }
+    public IFileSystemService FileSystem { get; }
+    public SearchService Search { get; }
+    public IIconService Icons { get; }
+    public IFileOperationService Operations { get; }
+    public MainViewModel Main { get; }
+
+    /// <summary>接入 Windows 外壳原版图标（imageres.dll / IShellItemImageFactory）。</summary>
+    private static IIconService CreateIconService(DispatcherQueue ui)
+    {
+        try
+        {
+            return new ShellIconService(ui);
+        }
+        catch
+        {
+            return new PlaceholderIconService();
+        }
+    }
+
+    /// <summary>接入文件操作队列引擎。</summary>
+    private static IFileOperationService CreateOperationService()
+    {
+        try
+        {
+            return new FileOperationService();
+        }
+        catch
+        {
+            return new PlaceholderOperationService();
+        }
+    }
+
+    /// <summary>接入 NTFS USN/MFT 索引（Everything 式极速搜索）。</summary>
+    public void WireSearchIndex()
+    {
+        Search.IndexFactory = volumeRoot =>
+        {
+            try
+            {
+                return new FluidExplorer.Services.Search.Usn.UsnVolumeIndex(volumeRoot);
+            }
+            catch
+            {
+                // 非 NTFS 卷等异常情况：该卷不建索引，搜索自动退化为实时扫描
+                return null;
+            }
+        };
+    }
+}