Marked `DocSignedNotification` as `[Obsolete]` with a note to use `Signature.Commands.SignCommand` instead. Removed the `PsPdfKitAnnotation` record and its associated `using` directives from `DocSignedNotification.cs`. Added missing `using EnvelopeGenerator.Application.Common.Dto;` to `AnnotationHandler.cs` and `DocStatusHandler.cs` to ensure proper DTO support.