Enhanced the `CreateEnvelopeWizardPopup` component:
- Added a new grid layout (`sender-create-wizard__body-layout`) to separate main content and side panel.
- Introduced a collapsible side panel for document upload and preview.
- Replaced old upload logic with `PdfFileDropZone` and added support for displaying document metadata (name, size) and replacement hints.
- Added asynchronous document preview rendering with `EnsureDocumentPreviewPreparedAsync`.
Localization updates:
- Added new localized strings for document upload hints in `de-DE`, `en-US`, and `fr-FR`.
CSS updates:
- Styled the new layout and side panel with transitions.
- Updated `PdfFileDropZone` styles for different states (e.g., document uploaded).
Refactored code for better maintainability and improved user feedback during document upload and preview preparation.
Replaced static upload message in `CreateEnvelopeWizardPopup.razor` with a new `PdfFileDropZone` component to enhance user experience. The component supports drag-and-drop functionality, file selection, and dynamic states (e.g., disabled, drag-active).
Introduced `PdfFileDropZone.razor` with customizable parameters such as `Disabled`, `HasDocument`, `UploadText`, and `DragDropHintText`. Added event handling for drag-and-drop interactions and file selection.
Updated `sender-page.css` to include styles for the new component, ensuring seamless integration with the existing layout. Adjusted styles for hover effects, drag-active state, and disabled state.
These changes improve usability and make PDF uploads more intuitive.
