feat(runtime): per-script execution timeout overriding the global default (#9)

Spec promised a per-script timeout but only the global ScriptExecutionTimeoutSeconds
existed. Add nullable TemplateScript.ExecutionTimeoutSeconds threaded through EF +
flattening (ResolvedScript) to ScriptExecutionActor/AlarmExecutionActor, which use
perScript ?? global for the execution CTS. Includes the EF migration for the new column.

src/ZB.MOM.WW.ScadaBridge.ConfigurationDatabase/Migrations/20260615183757_AddTemplateScriptExecutionTimeout.cs

@@ -0,0 +1,28 @@
+using Microsoft.EntityFrameworkCore.Migrations;
+
+#nullable disable
+
+namespace ZB.MOM.WW.ScadaBridge.ConfigurationDatabase.Migrations
+{
+    /// <inheritdoc />
+    public partial class AddTemplateScriptExecutionTimeout : Migration
+    {
+        /// <inheritdoc />
+        protected override void Up(MigrationBuilder migrationBuilder)
+        {
+            migrationBuilder.AddColumn<int>(
+                name: "ExecutionTimeoutSeconds",
+                table: "TemplateScripts",
+                type: "int",
+                nullable: true);
+        }
+
+        /// <inheritdoc />
+        protected override void Down(MigrationBuilder migrationBuilder)
+        {
+            migrationBuilder.DropColumn(
+                name: "ExecutionTimeoutSeconds",
+                table: "TemplateScripts");
+        }
+    }
+}

src/ZB.MOM.WW.ScadaBridge.ConfigurationDatabase/Migrations/ScadaBridgeDbContextModelSnapshot.cs

@@ -1313,6 +1313,9 @@ namespace ZB.MOM.WW.ScadaBridge.ConfigurationDatabase.Migrations
                         .IsRequired()
                         .HasColumnType("nvarchar(max)");
 
+                    b.Property<int?>("ExecutionTimeoutSeconds")
+                        .HasColumnType("int");
+
                     b.Property<bool>("IsInherited")
                         .HasColumnType("bit");