Add DI setup for modular architecture

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.

src/core/DigitalData.TaskFlow.Application/DependencyInjection.cs

@@ -0,0 +1,14 @@
+using Microsoft.Extensions.Configuration;
+using Microsoft.Extensions.DependencyInjection;
+
+namespace DigitalData.TaskFlow.Application;
+
+public static class DependencyInjection
+{
+    public static IServiceCollection AddApplicationServices(this IServiceCollection services, IConfiguration configuration)
+    {
+        // Register application services here
+        // Example: services.AddSingleton<IMyService, MyService>();
+        return services;
+    }
+}

src/core/DigitalData.TaskFlow.Application/DigitalData.TaskFlow.Application.csproj

@@ -6,4 +6,13 @@
     <Nullable>enable</Nullable>
   </PropertyGroup>
 
+  <ItemGroup>
+    <PackageReference Include="Microsoft.Extensions.Configuration.Abstractions" Version="10.0.12" />
+    <PackageReference Include="Microsoft.Extensions.DependencyInjection.Abstractions" Version="10.0.12" />
+  </ItemGroup>
+
+  <ItemGroup>
+    <ProjectReference Include="..\DigitalData.TaskFlow.Domain\DigitalData.TaskFlow.Domain.csproj" />
+  </ItemGroup>
+
 </Project>