Add UUID and metadata support for PDF signing

Enhanced PDF signing with UUID and metadata handling:
- Added `UUID` and `OriginalDocumentSha256` to `PdfSignOptionsDto` and `PdfSignatureCheckItemDto`.
- Introduced `BusinessReason` to separate metadata from signature reasons.
- Updated `PdfDigitalSignatureService` to embed and parse metadata in signature reasons.
- Improved error handling to include metadata in validation results.
- Updated `PdfSignatureController` to handle `UUID` in signing requests.

Refactored PKCS#11 configuration:
- Replaced `LibraryPath` with `AssetsRootPath` for asset resolution.
- Added `ProxySocket` and `DefaultApplicationName` options.
- Clarified runtime behavior for asset resolution in `README.md`.

Updated documentation and examples to reflect these changes.

EnvelopeGenerator.Server/EnvelopeGenerator.Server/Controllers/PdfSignatureController.cs

@@ -13,6 +13,7 @@ public class PdfSignatureController(IPdfDigitalSignatureService signatureService
     public sealed class SignPdfForm
     {
         public IFormFile? File { get; set; }
+        public string? UUID { get; set; }
         public string? Name { get; set; }
         public string? Reason { get; set; }
         public string? Location { get; set; }
@@ -50,6 +51,7 @@ public class PdfSignatureController(IPdfDigitalSignatureService signatureService
 
         var signOptions = new PdfSignOptionsDto
         {
+            UUID = request.UUID,
             Name = request.Name,
             Reason = request.Reason,
             Location = request.Location,