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

code-reviews/DeploymentManager/findings.md

@@ -402,18 +402,20 @@ Add an `IConfiguration` parameter (or a configure callback) to
 
 **Resolution**
 
-Resolved 2026-05-16 (commit pending): added an
-`AddDeploymentManager(IServiceCollection, IConfiguration)` overload that binds
-`DeploymentManagerOptions` to the `ScadaLink:DeploymentManager` configuration
-section (exposed as `ServiceCollectionExtensions.OptionsSection`). The
-`Microsoft.Extensions.Options.ConfigurationExtensions` package was added to the
-project. The original parameterless overload is retained for callers/tests that
-do not bind configuration. Regression tests:
-`AddDeploymentManager_WithConfiguration_BindsDeploymentManagerOptions`,
-`AddDeploymentManager_WithConfiguration_MissingSection_UsesDefaults`. Note: a
-one-line follow-up in `Host/Program.cs` (call the new overload with
-`builder.Configuration`) is required to take effect at runtime — that file is
-outside this module's edit scope and is surfaced for the Host owner.
+Resolved 2026-05-16 (commit pending): `AddDeploymentManager()` now calls
+`services.AddOptions<DeploymentManagerOptions>()` so `IOptions<DeploymentManagerOptions>`
+is always resolvable, and `Host/Program.cs` binds the
+`ScadaLink:DeploymentManager` section (exposed as
+`ServiceCollectionExtensions.OptionsSection`) via
+`services.Configure<DeploymentManagerOptions>(...)` — the same pattern the Host
+uses for `SecurityOptions`/`InboundApiOptions`. An earlier attempt added an
+`AddDeploymentManager(IConfiguration)` overload; that was reverted because the
+project convention (enforced by `Host.Tests.OptionsTests`) forbids component
+`Add*` methods from depending on `IConfiguration` — the Host owns
+configuration binding. Regression tests:
+`AddDeploymentManager_RegistersResolvableOptions_WithDefaults`,
+`AddDeploymentManager_OptionsBindToConfigurationSection_AsTheHostWires`,
+`OptionsSection_MatchesTheConventionalComponentSectionPath`.
 
 ### DeploymentManager-009 — Misleading timeout comment on `DeleteInstanceAsync`