feat(scripts): add typed Parameters.Get<T>() helpers for script API

Replace raw dictionary casting with ScriptParameters wrapper that provides
Get<T>, Get<T?>, Get<T[]>, and Get<List<T>> with clear error messages,
numeric conversion, and JsonElement support for Inbound API parameters.

src/ScadaLink.SiteRuntime/Actors/ScriptExecutionActor.cs

@@ -4,6 +4,7 @@ using Microsoft.Extensions.DependencyInjection;
 using Microsoft.Extensions.Logging;
 using ScadaLink.Commons.Interfaces.Services;
 using ScadaLink.Commons.Messages.ScriptExecution;
+using ScadaLink.Commons.Types;
 using ScadaLink.HealthMonitoring;
 using ScadaLink.SiteRuntime.Scripts;
 
@@ -100,7 +101,7 @@ public class ScriptExecutionActor : ReceiveActor
                 var globals = new ScriptGlobals
                 {
                     Instance = context,
-                    Parameters = parameters ?? new Dictionary<string, object?>(),
+                    Parameters = new ScriptParameters(parameters ?? new Dictionary<string, object?>()),
                     CancellationToken = cts.Token
                 };