Phase 7: Integration surfaces — Inbound API, External System Gateway, Notification Service

Inbound API (WP-1–5):
- POST /api/{methodName} with X-API-Key auth (401/403)
- Parameter validation with extended type system (Object, List)
- Central script execution with configurable timeout
- Route.To() cross-site calls (Call, GetAttribute/SetAttribute batch)
- Failures-only logging

External System Gateway (WP-6–10):
- HTTP/REST client with JSON, API Key + Basic Auth
- Dual call modes: Call() synchronous, CachedCall() with S&F
- Error classification (transient: 5xx/408/429, permanent: 4xx)
- Database.Connection() (ADO.NET pooling) + Database.CachedWrite() (S&F)

Notification Service (WP-11–13):
- SMTP with OAuth2 Client Credentials + Basic Auth
- BCC delivery, plain text, token lifecycle
- Transient → S&F, permanent → returned to script
- ScriptRuntimeContext wired with ExternalSystem/Database/Notify APIs

Repository implementations: ExternalSystem, Notification, InboundApi, InstanceLocator
781 tests pass, zero warnings.

tests/ScadaLink.IntegrationTests/IntegrationSurfaceTests.cs

@@ -200,7 +200,10 @@ public class IntegrationSurfaceTests
         // Create a minimal context — we use Substitute.For<IActorRef> which is fine since
         // we won't exercise Akka functionality in these tests.
         var actorRef = Substitute.For<Akka.Actor.IActorRef>();
-        var sharedLibrary = Substitute.For<SiteRuntime.Scripts.SharedScriptLibrary>(
+        var compilationService = new SiteRuntime.Scripts.ScriptCompilationService(
+            Microsoft.Extensions.Logging.Abstractions.NullLogger<SiteRuntime.Scripts.ScriptCompilationService>.Instance);
+        var sharedLibrary = new SiteRuntime.Scripts.SharedScriptLibrary(
+            compilationService,
             Microsoft.Extensions.Logging.Abstractions.NullLogger<SiteRuntime.Scripts.SharedScriptLibrary>.Instance);
 
         return new SiteRuntime.Scripts.ScriptRuntimeContext(