Check for updates when tray menu opens

- Checks for updates in background when user clicks tray icon
- Shows clickable blue banner when update available
- Rate limited to once per hour to avoid spam
- Version 1.1.5

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

DellMonitorControl/MainWindow.xaml.cs

@@ -18,6 +18,8 @@ public partial class MainWindow : Window
     private List<(XMonitor Monitor, List<InputSourceOption> Options)> _loadedMonitors = new();
     private Storyboard? _spinnerStoryboard;
     private DispatcherTimer? _showLogButtonTimer;
+    private UpdateInfo? _pendingUpdate;
+    private DateTime _lastUpdateCheck = DateTime.MinValue;
 
     public MainWindow()
     {
@@ -53,12 +55,50 @@ public partial class MainWindow : Window
         };
         _showLogButtonTimer.Start();
 
+        // Check for updates in background (max once per hour)
+        if ((DateTime.Now - _lastUpdateCheck).TotalMinutes > 60)
+        {
+            _lastUpdateCheck = DateTime.Now;
+            _ = CheckForUpdatesAsync();
+        }
+
         Dispatcher.BeginInvoke(new Action(() =>
         {
             Top = workArea.Bottom - ActualHeight - 10;
         }), DispatcherPriority.Loaded);
     }
 
+    private async Task CheckForUpdatesAsync()
+    {
+        try
+        {
+            var update = await UpdateChecker.CheckForUpdateAsync();
+            if (update != null)
+            {
+                _pendingUpdate = update;
+                await Dispatcher.InvokeAsync(() => ShowUpdateBanner(update));
+            }
+        }
+        catch
+        {
+            // Silently ignore update check failures
+        }
+    }
+
+    private void ShowUpdateBanner(UpdateInfo update)
+    {
+        updateBanner.Visibility = Visibility.Visible;
+        updateText.Text = $"v{update.LatestVersion} available - Click to update";
+    }
+
+    private void UpdateBanner_Click(object sender, System.Windows.Input.MouseButtonEventArgs e)
+    {
+        if (_pendingUpdate != null && !string.IsNullOrEmpty(_pendingUpdate.DownloadUrl))
+        {
+            UpdateChecker.OpenDownloadPage(_pendingUpdate.DownloadUrl);
+        }
+    }
+
     private void Window_Deactivated(object sender, EventArgs e)
     {
         Hide();