deprecate(lmxproxy): move all LmxProxy code, tests, and docs to deprecated/

LmxProxy is no longer needed. Moved the entire lmxproxy/ workspace, DCL
adapter files, and related docs to deprecated/. Removed LmxProxy registration
from DataConnectionFactory, project reference from DCL, protocol option from
UI, and cleaned up all requirement docs.

deprecated/ILmxProxyClient.cs

@@ -0,0 +1,43 @@
+using ZB.MOM.WW.LmxProxy.Client.Domain;
+
+namespace ScadaLink.DataConnectionLayer.Adapters;
+
+/// <summary>
+/// Subscription handle returned by <see cref="ILmxProxyClient.SubscribeAsync"/>.
+/// Disposing the subscription stops receiving updates.
+/// </summary>
+public interface ILmxSubscription : IAsyncDisposable { }
+
+/// <summary>
+/// Abstraction over the LmxProxy SDK client for testability.
+/// The production implementation delegates to the real
+/// <see cref="ZB.MOM.WW.LmxProxy.Client.LmxProxyClient"/> library.
+/// </summary>
+public interface ILmxProxyClient : IAsyncDisposable
+{
+    bool IsConnected { get; }
+
+    Task ConnectAsync(CancellationToken cancellationToken = default);
+    Task DisconnectAsync();
+
+    Task<Vtq> ReadAsync(string address, CancellationToken cancellationToken = default);
+    Task<IDictionary<string, Vtq>> ReadBatchAsync(IEnumerable<string> addresses, CancellationToken cancellationToken = default);
+
+    Task WriteAsync(string address, TypedValue value, CancellationToken cancellationToken = default);
+    Task WriteBatchAsync(IDictionary<string, TypedValue> values, CancellationToken cancellationToken = default);
+
+    Task<ILmxSubscription> SubscribeAsync(
+        IEnumerable<string> addresses,
+        Action<string, Vtq> onUpdate,
+        Action<Exception>? onStreamError = null,
+        CancellationToken cancellationToken = default);
+}
+
+/// <summary>
+/// Factory for creating <see cref="ILmxProxyClient"/> instances configured
+/// with host, port, and optional API key.
+/// </summary>
+public interface ILmxProxyClientFactory
+{
+    ILmxProxyClient Create(string host, int port, string? apiKey, bool useTls = false);
+}