Refactor and enhance Download Manager application

- Added new services: IContentDialogService, ISnackbarService
- Replaced DashboardPage and DashboardViewModel with DownloadingPage, DownloadingPageViewModel, WaitingPage, and WaitingPageViewModel
- Introduced AddNewTaskPage and AddNewTaskViewModel
- Replaced DownloadServiceManger with DownloadManagerService
- Updated WPF-UI package to 3.0.4 and added HtmlAgilityPack 1.11.61
- Refactored DownloadWorker to use async methods and added retry logic
- Converted DownloadItemData to partial class with ObservableProperty attributes
- Changed initial navigation page to DownloadingPage
- Updated MainWindow navigation items and title
- Added new utility classes: DoubleUtilities, MD5Utilities, StringExtension
- Added new XAML pages and ViewModels for task management and display
- Removed obsolete DashboardPage and related files

Models/UrlGetter/UrlGetterFactory.cs

@@ -0,0 +1,15 @@
+namespace DownloadManager.Models.UrlGetter
+{
+    public class UrlGetterFactory
+    {
+        public static IUrlGetter CreateUrlGetter(UrlGetterType type)
+        {
+            return type switch
+            {
+                UrlGetterType.Direct => new DirectUrlGetter(),
+                UrlGetterType.Yande => new YandeUrlGetter(),
+                _ => throw new ArgumentException("Invalid UrlGetterType"),
+            };
+        }
+    }
+}