Add cross-platform OPC UA client stack: shared library, CLI tool, and Avalonia UI

Implements Client.Shared (IOpcUaClientService with connection lifecycle, failover,
browse, read/write, subscriptions, alarms, history, redundancy), Client.CLI (8 CliFx
commands mirroring tools/opcuacli-dotnet), and Client.UI (Avalonia desktop app with
tree browser, read/write, subscriptions, alarms, and history tabs). All three target
.NET 10 and are covered by 249 unit tests.

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

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

@@ -0,0 +1,18 @@
+using ZB.MOM.WW.LmxOpcUa.Client.Shared;
+
+namespace ZB.MOM.WW.LmxOpcUa.Client.UI.Tests.Fakes;
+
+/// <summary>
+/// Fake factory that returns a preconfigured FakeOpcUaClientService.
+/// </summary>
+public sealed class FakeOpcUaClientServiceFactory : IOpcUaClientServiceFactory
+{
+    private readonly FakeOpcUaClientService _service;
+
+    public FakeOpcUaClientServiceFactory(FakeOpcUaClientService service)
+    {
+        _service = service;
+    }
+
+    public IOpcUaClientService Create() => _service;
+}