feat: wire ExternalSystem, Database, and Notify APIs into script runtime

IServiceProvider now flows through the actor chain (DeploymentManagerActor
→ InstanceActor → ScriptActor → ScriptExecutionActor) so scripts can
resolve IExternalSystemClient, IDatabaseGateway, and
INotificationDeliveryService from DI. ScriptGlobals exposes ExternalSystem,
Database, Notify, and Scripts as top-level properties so scripts can use
them without the Instance. prefix.

src/ScadaLink.SiteRuntime/Actors/DeploymentManagerActor.cs

@@ -32,6 +32,7 @@ public class DeploymentManagerActor : ReceiveActor, IWithTimers
     private readonly ILogger<DeploymentManagerActor> _logger;
     private readonly IActorRef? _dclManager;
     private readonly ISiteHealthCollector? _healthCollector;
+    private readonly IServiceProvider? _serviceProvider;
     private readonly Dictionary<string, IActorRef> _instanceActors = new();
     private int _totalDeployedCount;
 
@@ -45,7 +46,8 @@ public class DeploymentManagerActor : ReceiveActor, IWithTimers
         SiteRuntimeOptions options,
         ILogger<DeploymentManagerActor> logger,
         IActorRef? dclManager = null,
-        ISiteHealthCollector? healthCollector = null)
+        ISiteHealthCollector? healthCollector = null,
+        IServiceProvider? serviceProvider = null)
     {
         _storage = storage;
         _compilationService = compilationService;
@@ -54,6 +56,7 @@ public class DeploymentManagerActor : ReceiveActor, IWithTimers
         _options = options;
         _dclManager = dclManager;
         _healthCollector = healthCollector;
+        _serviceProvider = serviceProvider;
         _logger = logger;
 
         // Lifecycle commands
@@ -561,7 +564,8 @@ public class DeploymentManagerActor : ReceiveActor, IWithTimers
             _options,
             loggerFactory.CreateLogger<InstanceActor>(),
             _dclManager,
-            _healthCollector));
+            _healthCollector,
+            _serviceProvider));
 
         var actorRef = Context.ActorOf(props, instanceName);
         _instanceActors[instanceName] = actorRef;