fix(host,deployment-manager,communication): repair cross-module DI regressions from batch 1-2

- DeploymentManager-008: revert IConfiguration overload (violated OptionsTests
  component-convention); Host now binds the ScadaLink:DeploymentManager section
- SiteStreamGrpcServer: make test-only int ctor internal so DI sees one public
  ctor (resolves ambiguous-constructor failure in SiteCompositionRootTests)
- Host site composition-root test config: supply Cluster:SeedNodes for the new
  ClusterOptionsValidator

src/ScadaLink.Host/Program.cs

@@ -106,6 +106,8 @@ try
         SiteServiceRegistration.BindSharedOptions(builder.Services, builder.Configuration);
         builder.Services.Configure<SecurityOptions>(builder.Configuration.GetSection("ScadaLink:Security"));
         builder.Services.Configure<InboundApiOptions>(builder.Configuration.GetSection("ScadaLink:InboundApi"));
+        builder.Services.Configure<DeploymentManagerOptions>(
+            builder.Configuration.GetSection(ScadaLink.DeploymentManager.ServiceCollectionExtensions.OptionsSection));
 
         var app = builder.Build();