Fix build errors

src/GuiApp/Avalonia/FileTime.GuiApp/Services/SystemClipboardService.cs

@@ -1,3 +1,5 @@
+using Avalonia;
+using Avalonia.Input.Platform;
 using FileTime.App.Core.Services;
 
 namespace FileTime.GuiApp.Services;
@@ -6,7 +8,8 @@ public class SystemClipboardService : ISystemClipboardService
 {
     public async Task CopyToClipboardAsync(string text)
     {
-        if (global::Avalonia.Application.Current?.Clipboard is { } clipboard)
+        var clipboard = AvaloniaLocator.Current.GetService<IClipboard>();
+        if (clipboard is not null)
         {
             await clipboard.SetTextAsync(text);
         }