Refactor and enhance DownloadManager application

Refactored and enhanced the DownloadManager application with significant updates across multiple files. Key changes include:

- **App.xaml.cs**: Re-added necessary imports, updated service registrations, and made `OnStartup` asynchronous.
- **DownloadManager.csproj**: Updated target framework, application icon, and added assembly version.
- **DownloadManager.sln**: Updated project format and added configurations for multiple platforms.
- **DownloadManagerService.cs**: Added `HistoryStorageService` dependency, introduced `Initial` method, and improved task management.
- **DownloadWorker.cs**: Enhanced error handling and changed `StartDownloadAsync` to `StartDownload`.
- **ViewModels**: Refactored to use dependency injection, updated task initialization, and added new commands for settings management.
- **UI Updates**: Improved `DownloadingPage.xaml` and `WaitingPage.xaml` with `ListView` and added headers. Restructured `SettingsPage.xaml` for better organization and added new settings options.
- **MainWindow**: Enhanced navigation and applied user-defined themes and backdrops.
- **New Files**: Added `HistoryStorageService.cs`, `ThemeToIndexConverter.cs`, `CompletedItemData.cs`, `Settings.Designer.cs`, `Settings.settings`, `Constants.cs`, `CompletedPageViewModel.cs`, `CompletedPage.xaml`, and `CompletedPage.xaml.cs` to support new features and improvements.

These changes aim to improve the application's robustness, maintainability, and user experience.

DownloaderCore/DownloadWorker.cs

@@ -3,7 +3,6 @@ using DownloadManager.Models;
 using DownloadManager.Models.UrlGetter;
 using DownloadManager.Utilities;
 using System.ComponentModel;
-using System.Diagnostics;
 using System.IO;
 
 namespace DownloadManager.DownloaderCore;
@@ -13,6 +12,8 @@ public class DownloadWorker(DownloadItemData itemData)
     private DownloadItemData _downloadData = itemData;
     public DownloadItemData DownloadData => _downloadData;
 
+    public string errorMessage = string.Empty;
+
     public Action? OnDownloadStarted;
     public Action? OnDownloadFileCompleted;
     public Action? OnDownloadStop;
@@ -77,12 +78,14 @@ public class DownloadWorker(DownloadItemData itemData)
         if (e.Error != null)
         {
             _downloadData.Status = DownloadStatus.Failed;
-            throw e.Error;
+            errorMessage = e.Error.Message;
+            //throw e.Error;
         }
         else
         {
             _downloadData.Status = DownloadStatus.Completed;
             _worker!.Dispose();
+            _worker = null;
 
             // Check md5
             if (_downloadData.MD5 != null)
@@ -109,7 +112,7 @@ public class DownloadWorker(DownloadItemData itemData)
             await Task.Delay(1000);
 
             await BuildDownloadRequestAsync();
-            StartDownloadAsync();
+            StartDownload();
 
             return true;
         }
@@ -120,7 +123,7 @@ public class DownloadWorker(DownloadItemData itemData)
         }
     }
 
-    public void StartDownloadAsync()
+    public void StartDownload()
     {
         if (_worker == null)
             return;