Introduced `DependencyInjection.cs` in Application and Infrastructure layers to centralize service registration. Updated project files to include necessary package references (`Microsoft.Extensions.Configuration.Abstractions` and `Microsoft.Extensions.DependencyInjection.Abstractions`) and project dependencies between layers. Integrated service registration in `Program.cs` to enable modular architecture for the API.
Added three new projects: `DigitalData.TaskFlow.Domain`,
`DigitalData.TaskFlow.Application`, and
`DigitalData.TaskFlow.Infrastructure` to the solution.
Updated the solution file to include their paths, GUIDs,
build configurations, and nested structure.
Each project targets `.NET 8.0`, uses `Microsoft.NET.Sdk`,
and enables implicit usings and nullable reference types.
Introduced an `ExtensibilityGlobals` section with a
`SolutionGuid` for better solution management.
