Add UI features, alarm ack, historian UTC fix, and Client.UI documentation

Major changes across the client stack:
- Settings persistence (connection, subscriptions, alarm source)
- Deferred OPC UA SDK init for instant startup
- Array/status code formatting, write value popup, alarm acknowledgment
- Severity-colored alarm rows, condition dedup on server side
- DateTimeRangePicker control with preset buttons and UTC text input
- Historian queries use wwTimezone=UTC and OPCQuality column
- Recursive subscribe from tree, multi-select remove
- Connection panel with expander, folder chooser for cert path
- Dynamic tab headers showing subscription/alarm counts
- Client.UI.md documentation with headless-rendered screenshots

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

src/ZB.MOM.WW.LmxOpcUa.Client.UI/Views/AlarmsView.axaml.cs

@@ -1,11 +1,79 @@
+using System.ComponentModel;
 using Avalonia.Controls;
+using Avalonia.Interactivity;
+using Avalonia.Media;
+using Avalonia.VisualTree;
+using ZB.MOM.WW.LmxOpcUa.Client.UI.ViewModels;
 
 namespace ZB.MOM.WW.LmxOpcUa.Client.UI.Views;
 
 public partial class AlarmsView : UserControl
 {
+    // Severity color bands (OPC UA severity 0-1000)
+    private static readonly IBrush InactiveBrush = new SolidColorBrush(Color.Parse("#F0F0F0"));     // light grey
+    private static readonly IBrush LowBrush = new SolidColorBrush(Color.Parse("#DBEAFE"));          // light blue (1-332)
+    private static readonly IBrush MediumBrush = new SolidColorBrush(Color.Parse("#FEF3C7"));       // light yellow (333-665)
+    private static readonly IBrush HighBrush = new SolidColorBrush(Color.Parse("#FEE2E2"));         // light red (666-899)
+    private static readonly IBrush CriticalBrush = new SolidColorBrush(Color.Parse("#FECACA"));     // red (900-1000)
+
     public AlarmsView()
     {
         InitializeComponent();
     }
-}
+
+    protected override void OnLoaded(RoutedEventArgs e)
+    {
+        base.OnLoaded(e);
+
+        var grid = this.FindControl<DataGrid>("AlarmsGrid");
+        if (grid == null) return;
+
+        var contextMenu = new ContextMenu();
+        var ackItem = new MenuItem { Header = "Acknowledge..." };
+        ackItem.Click += OnAcknowledgeClicked;
+        contextMenu.Items.Add(ackItem);
+        contextMenu.Opening += OnContextMenuOpening;
+        grid.ContextMenu = contextMenu;
+    }
+
+    private void OnDataGridLoadingRow(object? sender, DataGridRowEventArgs e)
+    {
+        if (e.Row.DataContext is AlarmEventViewModel alarm)
+            e.Row.Background = GetSeverityBrush(alarm);
+    }
+
+    private static IBrush GetSeverityBrush(AlarmEventViewModel alarm)
+    {
+        if (!alarm.ActiveState)
+            return InactiveBrush;
+
+        return alarm.Severity switch
+        {
+            >= 900 => CriticalBrush,
+            >= 666 => HighBrush,
+            >= 333 => MediumBrush,
+            _ => LowBrush
+        };
+    }
+
+    private void OnContextMenuOpening(object? sender, CancelEventArgs e)
+    {
+        var grid = this.FindControl<DataGrid>("AlarmsGrid");
+        if (grid?.SelectedItem is not AlarmEventViewModel alarm || !alarm.CanAcknowledge)
+            e.Cancel = true;
+    }
+
+    private void OnAcknowledgeClicked(object? sender, RoutedEventArgs e)
+    {
+        if (DataContext is not AlarmsViewModel vm) return;
+
+        var grid = this.FindControl<DataGrid>("AlarmsGrid");
+        if (grid?.SelectedItem is not AlarmEventViewModel alarm || !alarm.CanAcknowledge) return;
+
+        var parentWindow = this.FindAncestorOfType<Window>();
+        if (parentWindow == null) return;
+
+        var ackWindow = new AckAlarmWindow(vm, alarm);
+        ackWindow.ShowDialog(parentWindow);
+    }
+}