Add configurable transport security profiles and bind address

Adds Security section to appsettings.json with configurable OPC UA
transport profiles (None, Basic256Sha256-Sign, Basic256Sha256-SignAndEncrypt),
certificate policy settings, and a configurable BindAddress for the
OPC UA endpoint. Defaults preserve backward compatibility.

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

tools/opcuacli-dotnet/Commands/WriteCommand.cs

@@ -21,6 +21,9 @@ public class WriteCommand : ICommand
     [CommandOption("password", 'P', Description = "Password for authentication")]
     public string? Password { get; init; }
 
+    [CommandOption("security", 'S', Description = "Transport security: none, sign, encrypt (default: none)")]
+    public string Security { get; init; } = "none";
+
     /// <summary>
     /// Gets the node identifier that should receive the write.
     /// </summary>
@@ -39,7 +42,7 @@ public class WriteCommand : ICommand
     /// <param name="console">The console used to report the write result.</param>
     public async ValueTask ExecuteAsync(IConsole console)
     {
-        using var session = await OpcUaHelper.ConnectAsync(Url, Username, Password);
+        using var session = await OpcUaHelper.ConnectAsync(Url, Username, Password, Security);
 
         var node = new NodeId(NodeId);
         var current = await session.ReadValueAsync(node);