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.Infrastructure.Crypt/resources/INFRASTRUCTURE_PLAN.md

@@ -234,7 +234,7 @@ EnvelopeGenerator.Infrastructure.Crypt/
 Use options (bound from host config) with environment override support:
 
 - `Crypt:Provider = PKCS11`
-- `Crypt:Pkcs11:LibraryPath`
+- `Crypt:Pkcs11:AssetsRootPath` (base path that contains bundled `pkcs11` assets)
 - `Crypt:Pkcs11:SlotId` or token selectors
 - `Crypt:Pkcs11:UserPin` (from secret store/env, not plain committed value)
 - `Crypt:Pkcs11:PrivateKeyLabel`
@@ -243,7 +243,7 @@ Use options (bound from host config) with environment override support:
 
 Validation rules:
 
-- library path required,
+- resolved module path must exist under configured/default assets root,
 - at least one key locator required,
 - pin required for signing operations.