Added a new nullable ReceiverSignature property to the RemoveSignatureNotification record
to support handling receiver-specific signature removal events.
- Implements INotificationHandler<RemoveSignatureNotification>
- Deletes Annotation entities matching the Envelope UUID from the repository
- Uses IRepository<Annotation> for data access
- Added `UnstructuredAnnotations` property to handle annotations without structured IDs
- Changed default `hasStructuredID` to `False`, set to `True` only after successful parsing
- Updated `AddInstantJSONAnnotationToPDF` to process annotations directly instead of grouping by receiver
- Simplified logic for reversing annotations and applying seal positioning
