Introduce four custom exceptions (BurnAnnotationException, CreateReportException, ExportDocumentException, MergeDocumentException) under EnvelopeGenerator.ServiceHost.Exceptions for improved error handling. Update the project file to include the new Extensions folder.
Created a new EnvelopeGenerator.ServiceHost project targeting .NET 8.0. Set up minimal API host with controllers, Swagger/OpenAPI support, and development configuration files. Updated solution to include the new project with appropriate build settings.
