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.Shared.Tests/Fakes/FakeApplicationConfigurationFactory.cs

@@ -0,0 +1,38 @@
+using Opc.Ua;
+using ZB.MOM.WW.LmxOpcUa.Client.Shared.Adapters;
+using ZB.MOM.WW.LmxOpcUa.Client.Shared.Models;
+
+namespace ZB.MOM.WW.LmxOpcUa.Client.Shared.Tests.Fakes;
+
+internal sealed class FakeApplicationConfigurationFactory : IApplicationConfigurationFactory
+{
+    public bool ThrowOnCreate { get; set; }
+    public int CreateCallCount { get; private set; }
+    public ConnectionSettings? LastSettings { get; private set; }
+
+    public Task<ApplicationConfiguration> CreateAsync(ConnectionSettings settings, CancellationToken ct)
+    {
+        CreateCallCount++;
+        LastSettings = settings;
+
+        if (ThrowOnCreate)
+            throw new InvalidOperationException("FakeApplicationConfigurationFactory configured to fail.");
+
+        var config = new ApplicationConfiguration
+        {
+            ApplicationName = "FakeClient",
+            ApplicationUri = "urn:localhost:FakeClient",
+            ApplicationType = ApplicationType.Client,
+            SecurityConfiguration = new SecurityConfiguration
+            {
+                AutoAcceptUntrustedCertificates = true
+            },
+            ClientConfiguration = new ClientConfiguration
+            {
+                DefaultSessionTimeout = settings.SessionTimeoutSeconds * 1000
+            }
+        };
+
+        return Task.FromResult(config);
+    }
+}