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/InstanceActor.cs

@@ -39,6 +39,7 @@ public class InstanceActor : ReceiveActor
     private readonly SiteRuntimeOptions _options;
     private readonly ILogger _logger;
     private readonly ISiteHealthCollector? _healthCollector;
+    private readonly IServiceProvider? _serviceProvider;
     private readonly Dictionary<string, object?> _attributes = new();
     private readonly Dictionary<string, string> _attributeQualities = new();
     private readonly Dictionary<string, AlarmState> _alarmStates = new();
@@ -64,7 +65,8 @@ public class InstanceActor : ReceiveActor
         SiteRuntimeOptions options,
         ILogger logger,
         IActorRef? dclManager = null,
-        ISiteHealthCollector? healthCollector = null)
+        ISiteHealthCollector? healthCollector = null,
+        IServiceProvider? serviceProvider = null)
     {
         _instanceUniqueName = instanceUniqueName;
         _storage = storage;
@@ -75,6 +77,7 @@ public class InstanceActor : ReceiveActor
         _logger = logger;
         _dclManager = dclManager;
         _healthCollector = healthCollector;
+        _serviceProvider = serviceProvider;
 
         // Deserialize the flattened configuration
         _configuration = JsonSerializer.Deserialize<FlattenedConfiguration>(configJson);
@@ -479,7 +482,8 @@ public class InstanceActor : ReceiveActor
                 _sharedScriptLibrary,
                 _options,
                 _logger,
-                _healthCollector));
+                _healthCollector,
+                _serviceProvider));
 
             var actorRef = Context.ActorOf(props, $"script-{script.CanonicalName}");
             _scriptActors[script.CanonicalName] = actorRef;