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/ApiKey.cs

@@ -0,0 +1,49 @@
+namespace ZB.MOM.WW.LmxProxy.Host.Security
+{
+    /// <summary>
+    ///     Represents an API key with associated permissions
+    /// </summary>
+    public class ApiKey
+    {
+        /// <summary>
+        ///     The API key value
+        /// </summary>
+        public string Key { get; set; } = string.Empty;
+
+        /// <summary>
+        ///     Description of what this API key is used for
+        /// </summary>
+        public string Description { get; set; } = string.Empty;
+
+        /// <summary>
+        ///     The role assigned to this API key
+        /// </summary>
+        public ApiKeyRole Role { get; set; } = ApiKeyRole.ReadOnly;
+
+        /// <summary>
+        ///     Whether this API key is enabled
+        /// </summary>
+        public bool Enabled { get; set; } = true;
+
+        /// <summary>
+        ///     Checks if the API key is valid
+        /// </summary>
+        public bool IsValid() => Enabled;
+    }
+
+    /// <summary>
+    ///     API key roles
+    /// </summary>
+    public enum ApiKeyRole
+    {
+        /// <summary>
+        ///     Can only read data
+        /// </summary>
+        ReadOnly,
+
+        /// <summary>
+        ///     Can read and write data
+        /// </summary>
+        ReadWrite
+    }
+}