Refactor PDF viewing and integrate DevExpress support

- Removed folder reference for "Controllers" in the project file.
- Updated `ViewPdf.cshtml` to include layout and clarify PDF output.
- Enhanced `ViewPdf.cshtml.cs` with improved logging and error handling.
- Added MVC controller services in `Program.cs` for DevExpress functionality.
- Introduced `DocumentViewerController` to manage document viewing requests.

DXApp.TemplateKitProject/Program.cs

@@ -8,6 +8,9 @@ using DevExpress.XtraReports.Web.Extensions;
 
 var builder = WebApplication.CreateBuilder(args);
 
+// MVC-Controller hinzufügen (benötigt für DevExpress WebDocumentViewer)
+builder.Services.AddControllersWithViews();
+
 builder.Services.AddRazorPages();
 
 // DevExpress Controls und Reporting Services
@@ -52,5 +55,8 @@ app.UseDevExpressControls();
 
 app.UseRouting();
 app.UseAuthorization();
+
+// Controller-Routen verfügbar machen (wichtig für DevExpress WebDocumentViewer)
+app.MapControllers();
 app.MapRazorPages();
 app.Run();