Refactor `EnvelopeSenderEditorPage.razor` to enhance the structure and behavior of the PDF editor wrapper:
- Add `class="pdf-editor-wrapper"` and update `overflow` to `auto`.
- Update `DxPdfViewer`'s `CssClass` to `sender-editor-pdf-viewer`.
- Introduce `OnAfterRenderAsync` to synchronize the overlay with the viewer.
Add new styles in `envelope-viewer.css` for better layout:
- Ensure `.pdf-editor-wrapper` and `.sender-editor-pdf-viewer` occupy full dimensions.
- Center and align content within the PDF viewer.
Enhance `envelope-editor.js` with `syncOverlayToPage`:
- Dynamically adjust overlay position and size relative to the viewer.
- Use `MutationObserver` and event listeners for real-time synchronization.
- Handle delayed rendering with scheduled sync attempts.
These changes improve overlay alignment, user experience, and code maintainability.
Introduced a new Blazor page `EnvelopeSenderEditorPage.razor` for editing envelopes with an interactive interface. Integrated `DxPdfViewer` for rendering PDFs and added functionality for uploading, viewing, and interacting with PDF files.
Key features:
- Action bar with buttons for uploading PDFs, toggling signature placement mode, clearing fields, and saving.
- Placement mode for adding signature fields via an overlay, with visual placeholders.
- JavaScript interop (`envelope-editor.js`) for precise click coordinate mapping.
- Error handling for unsupported file types and size limits (50 MB).
- Logging for debugging key actions like PDF uploads and field placements.
Defined constants for accurate signature field dimensions and scaling. Added models (`SignatureFieldDraft`, `OverlayCoords`) to manage state and interactions.
