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>

tests/ZB.MOM.WW.LmxOpcUa.Client.UI.Tests/Fakes/FakeSettingsService.cs

@@ -0,0 +1,23 @@
+using ZB.MOM.WW.LmxOpcUa.Client.UI.Services;
+
+namespace ZB.MOM.WW.LmxOpcUa.Client.UI.Tests.Fakes;
+
+public sealed class FakeSettingsService : ISettingsService
+{
+    public UserSettings Settings { get; set; } = new();
+    public int LoadCallCount { get; private set; }
+    public int SaveCallCount { get; private set; }
+    public UserSettings? LastSaved { get; private set; }
+
+    public UserSettings Load()
+    {
+        LoadCallCount++;
+        return Settings;
+    }
+
+    public void Save(UserSettings settings)
+    {
+        SaveCallCount++;
+        LastSaved = settings;
+    }
+}