Replaced `DxPdfViewer` with a custom PDF rendering solution in `SenderPdfImageEditor` to improve flexibility and control. Added support for displaying placeholder messages and interactive signature fields. Introduced the `SenderPdfFieldOverlay` record to encapsulate field data.
Updated `SenderEditorPage` logic to manage page counts, image URLs, and field overlays. Added a method to estimate PDF page counts. Refactored field removal logic to use index-based operations.
Enhanced styling in `envelope-viewer.css` for improved layout and responsiveness. Updated localization files with new strings for page labels and placeholders. Adjusted JavaScript selectors in `envelope-editor.js` to support the new rendering approach.
Introduced a new `SenderEditorPage` with a modern UI for managing envelopes, uploading PDFs, and placing signature fields. Integrated `DevExpress.Blazor.PdfViewer` for PDF rendering and interaction.
Key features include:
- PDF upload, rendering, and validation.
- Signature field placement with normalized coordinates.
- Receiver management with validation and email suggestions.
- Envelope metadata handling (title, message).
- Save as draft and send functionality with validation.
- Edit mode for existing envelopes.
- Improved UX with dynamic elements and color-coded receivers.
- Localization support for multi-language UI.
Updated `_Imports.razor` to include necessary namespaces for DevExpress components and the new `PdfEditor` namespace.
