feat(PDFBurner): support unstructured annotations and simplify processing

- 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

EnvelopeGenerator.Web/wwwroot/js/app.js

@@ -275,7 +275,6 @@ class App {
         });
     }
 
-
     async validateAnnotations(totalSignatures) {
         const annotations = await getAnnotations(this.pdfKit)
         const filtered = annotations