Updated namespaces for DTOs and services to improve project organization. Marked several interfaces as obsolete in favor of MediatR for better request handling. Simplified `BaseUpdateDto` and other DTOs by removing `IUnique<int>` implementation. Changed return types of `CreateAsync` methods to return corresponding read DTOs. Removed reference to `DigitalData.Core.DTO` in the project file, reflecting a shift in architecture for maintainability.
