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/lmxproxy/src-reference/ZB.MOM.WW.LmxProxy.Host/Security/ApiKeyConfiguration.cs

@@ -0,0 +1,15 @@
+using System.Collections.Generic;
+
+namespace ZB.MOM.WW.LmxProxy.Host.Security
+{
+    /// <summary>
+    ///     Configuration for API keys loaded from file
+    /// </summary>
+    public class ApiKeyConfiguration
+    {
+        /// <summary>
+        ///     List of API keys
+        /// </summary>
+        public List<ApiKey> ApiKeys { get; set; } = new();
+    }
+}