fix: pass Configuration property to all ProjectReferences

The Integration.Tests projects were being built in Debug mode even when
the solution was built in Release mode, causing CycloneDX.MSBuild to be
built twice simultaneously (once in Release, once in Debug), resulting in
file locking on CycloneDX.MSBuild.deps.json.

Changes:
- Add Configuration=$(Configuration) to all Integration.Tests ProjectReferences
- Add Configuration=$(Configuration) to CycloneDX.MSBuild ProjectReference
- This ensures all referenced projects build with the same configuration
  as the parent test project

Build output showed the problem:
1. CycloneDX.MSBuild -> .../bin/Release/... (correct)
2. CycloneDX.MSBuild -> .../bin/Debug/... (wrong - caused by Integration.Tests)
3. DisabledProject -> .../bin/Debug/... (wrong - should be Release)

Now all projects build with the same configuration, preventing simultaneous
Release and Debug builds of the shared dependency.

Author: claude

tests/CycloneDX.MSBuild.Tests/CycloneDX.MSBuild.Tests.csproj

@@ -31,22 +31,26 @@
     <ProjectReference Include="../../src/CycloneDX.MSBuild/CycloneDX.MSBuild.csproj">
       <ReferenceOutputAssembly>false</ReferenceOutputAssembly>
       <BuildInParallel>false</BuildInParallel>
-      <Properties>GeneratePackageOnBuild=false</Properties>
+      <Properties>GeneratePackageOnBuild=false;Configuration=$(Configuration)</Properties>
     </ProjectReference>
 
     <!-- Reference the test projects to ensure they're built before copying -->
     <!-- Disable parallel builds to prevent file locking on shared CycloneDX.MSBuild dependency -->
+    <!-- Pass Configuration to ensure all projects build with the same configuration -->
     <ProjectReference Include="../Integration.Tests/SimpleProject/SimpleProject.csproj">
       <ReferenceOutputAssembly>false</ReferenceOutputAssembly>
       <BuildInParallel>false</BuildInParallel>
+      <Properties>Configuration=$(Configuration)</Properties>
     </ProjectReference>
     <ProjectReference Include="../Integration.Tests/MultiTargetProject/MultiTargetProject.csproj">
       <ReferenceOutputAssembly>false</ReferenceOutputAssembly>
       <BuildInParallel>false</BuildInParallel>
+      <Properties>Configuration=$(Configuration)</Properties>
     </ProjectReference>
     <ProjectReference Include="../Integration.Tests/DisabledProject/DisabledProject.csproj">
       <ReferenceOutputAssembly>false</ReferenceOutputAssembly>
       <BuildInParallel>false</BuildInParallel>
+      <Properties>Configuration=$(Configuration)</Properties>
     </ProjectReference>
   </ItemGroup>