feat(ui): add sticky version label to variables pane\n\n- Split left SplitView pane into scroll area + bottom bar\n- Show current app version from AssemblyInformationalVersion\n- Uses theme surface + top border per design tokens

src/AdvancedCalculator/ViewModels/MainViewModel.cs

@@ -6,6 +6,7 @@ using AdvancedCalculator.Models;
 using AdvancedCalculator.Services;
 using CSMic;
 using System;
+using System.Reflection;
 
 namespace AdvancedCalculator.ViewModels;
 
@@ -42,6 +43,12 @@ public partial class MainViewModel : ViewModelBase
     public ObservableCollection<HistoryItem> History { get; }
     public ObservableCollection<VariableItem> Variables { get; }
 
+    // App version string, sourced from AssemblyInformationalVersion
+    public string AppVersion { get; } =
+        typeof(MainViewModel).Assembly
+            .GetCustomAttribute<AssemblyInformationalVersionAttribute>()?
+            .InformationalVersion ?? "0.0.0";
+
     [RelayCommand]
     private void ToggleFunctions()
     {