refactor: Make Domain exceptions serializable and add XML docs

- Add [Serializable] attribute to all custom exceptions
- Add protected constructors for serialization support
- Add XML documentation comments
- Update SwissQrCodeNotFoundException message format

DocumentOperator.Domain/Exceptions/SwissQrCodeNotFoundException.cs

@@ -3,6 +3,7 @@ namespace DocumentOperator.Domain.Exceptions;
 /// <summary>
 /// Exception thrown when a Swiss QR Code cannot be found in a PDF document.
 /// </summary>
+[Obsolete("This exception is deprecated. Use SwissQrCodeNotFoundException instead.")]
 public sealed class SwissQrCodeNotFoundException : Exception
 {
     public SwissQrCodeNotFoundException()