The `dx-blazor-reporting-components.bs5.css` file reference was removed from `EnvelopeReceiverPage_DxPdfViewer.razor`. This CSS file was likely used for styling DevExpress Blazor Reporting Viewer components, which are no longer needed or have been replaced.
Added a new Razor page `EnvelopeReceiverPage_DxPdfViewer.razor` with a route `/envelope/DxPdfViewer`. Integrated DevExpress components, including `DxPdfViewer` for displaying PDF documents and `DxFileInput` for drag-and-drop file uploads. Styled the drag-and-drop zone with custom CSS. Initialized the viewer with a default embedded PDF file and implemented logic to handle file uploads dynamically.
