Enabled multi-targeting in `DocumentService.Application` to support `net462`, `net480`, and `net8.0`. Updated dependencies with framework-specific versions and added conditional configurations for compatibility.
Refactored `DocumentService.Client` by removing redundant enums and unused code. Adjusted namespaces and project references to streamline the codebase and improve maintainability.
These changes modernize the project, enhance compatibility, and align with modular design principles.
Introduced a new `DocumentService.Client` project targeting `net462`, `net480`, and `net8.0`. The project includes metadata for NuGet packaging, such as `PackageId`, `Authors`, and `Company`, and references `Microsoft.Extensions.DependencyInjection` and `Microsoft.Extensions.Logging`.
Updated `DocumentService.sln` to include the new project, its build configurations, and solution folder associations.
Added `icon.png` as the NuGet package icon and included it in the project file.
