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.

Models/CompletedItemData.cs

@@ -0,0 +1,12 @@
+namespace DownloadManager.Models
+{
+    public struct CompletedItemData
+    {
+        public string Name { get; set; }
+        public string Url { get; set; }
+        public string SavePath { get; set; }
+        public string FullName { get; set; }
+        public string Status { get; set; }
+        public string ErrorMessage { get; set; }
+    }
+}

Models/DownloadItemData.cs

@@ -19,7 +19,7 @@ public partial class DownloadItemData : ObservableObject
     }
 
     [ObservableProperty]
-    private string? fileName;
+    private string fileName = string.Empty;
 
     [ObservableProperty]
     private string filePath;

Models/UrlGetter/UrlGetterType.cs

@@ -9,4 +9,4 @@ namespace DownloadManager.Models.UrlGetter
         [Description("Yande post URL")]
         Yande,
     }
-}
+}

Models/UrlGetter/YandeUrlGetter.cs

@@ -7,7 +7,7 @@ using System.Text.Json;
 namespace DownloadManager.Models.UrlGetter;
 public class YandeUrlGetter : IUrlGetter
 {
-    readonly HttpClient client = new ();
+    readonly HttpClient client = new();
     const int maxRetries = 3;
     const int delayMilliseconds = 1000;
 
@@ -16,7 +16,7 @@ public class YandeUrlGetter : IUrlGetter
         // Get the ID of the post from the URL
         var id = taskUrl.Split("https://yande.re/post/show/").Last();
 
-        for (int attempt = 0; attempt < maxRetries; attempt++)
+        for (var attempt = 0; attempt < maxRetries; attempt++)
         {
             try
             {
@@ -36,13 +36,14 @@ public class YandeUrlGetter : IUrlGetter
                         return new FileUrl(null, null, null);
                     }
 
-                    if (!firstElement.TryGetProperty("md5", out var md5Element))
-                    {
-                        return new FileUrl(null, null, null);
-                    }
-
                     var fileUrl = fileUrlElement.GetString();
                     var fileName = Path.GetFileName(fileUrl)?.ToUnescapedString();
+
+                    if (!firstElement.TryGetProperty("md5", out var md5Element))
+                    {
+                        return new FileUrl(fileUrl, fileName, null);
+                    }
+
                     var md5 = md5Element.GetString();
 
                     return new FileUrl(fileUrl, fileName, md5);