Add RecClientTestBase for integration testing setup

Introduce `RecClientTestBase` to streamline integration tests for `ReCClient`.
This abstract class uses `WebApplicationFactory` to create a test server
for `ReC.API` and configures a `ServiceProvider` with necessary services.
It includes helper methods for creating scoped `ReCClient` instances and
ensures proper resource cleanup via `IDisposable`.

Update `ReC.Tests.csproj` to include:
- `Microsoft.AspNetCore.Mvc.Testing` package for integration testing.
- Project references to `ReC.API` and `ReC.Client` for testing purposes.

These changes establish a reusable and maintainable testing infrastructure.

tests/ReC.Tests/ReC.Tests.csproj

@@ -12,6 +12,7 @@
   <ItemGroup>
     <PackageReference Include="coverlet.collector" Version="6.0.0" />
     <PackageReference Include="MediatR" Version="14.0.0" />
+    <PackageReference Include="Microsoft.AspNetCore.Mvc.Testing" Version="8.0.0" />
     <PackageReference Include="Microsoft.NET.Test.Sdk" Version="17.8.0" />
     <PackageReference Include="Microsoft.Extensions.Configuration.Json" Version="10.0.0" />
     <PackageReference Include="Moq" Version="4.20.72" />
@@ -21,7 +22,9 @@
   </ItemGroup>
 
   <ItemGroup>
+    <ProjectReference Include="..\..\src\ReC.API\ReC.API.csproj" />
     <ProjectReference Include="..\..\src\ReC.Application\ReC.Application.csproj" />
+    <ProjectReference Include="..\..\src\ReC.Client\ReC.Client.csproj" />
     <ProjectReference Include="..\..\src\ReC.Infrastructure\ReC.Infrastructure.csproj" />
     <ProjectReference Include="..\..\src\ReC.Domain\ReC.Domain.csproj" />
   </ItemGroup>