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.Application/Common/Dto/PdfSignatureCheckResultDto.cs

@@ -25,6 +25,7 @@ public sealed record PdfSignatureCertificateInfoDto(
 public sealed record PdfSignatureCheckItemDto(
     bool CoversWholeDoc,
     string? Reason,
+    string? BusinessReason,
     string? Location,
     string? DeclaredName,
     string? ContactInfo,
@@ -44,6 +45,8 @@ public sealed record PdfSignatureCheckItemDto(
     string? Filter,
     string? SubFilter,
     string? ApplicationName,
+    string? UUID,
+    string? OriginalDocumentSha256,
     string? MessageDigestHex,
     string? Error);