feat(lmxproxy): phase 1 — v2 protocol types and domain model

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

lmxproxy/src-reference/ZB.MOM.WW.LmxProxy.Host/Configuration/SubscriptionConfiguration.cs

@@ -0,0 +1,18 @@
+namespace ZB.MOM.WW.LmxProxy.Host.Configuration
+{
+    /// <summary>
+    ///     Configuration for subscription management
+    /// </summary>
+    public class SubscriptionConfiguration
+    {
+        /// <summary>
+        ///     Buffer size for each client's channel (number of messages)
+        /// </summary>
+        public int ChannelCapacity { get; set; } = 1000;
+
+        /// <summary>
+        ///     Strategy when channel buffer is full: "DropOldest", "DropNewest", or "Wait"
+        /// </summary>
+        public string ChannelFullMode { get; set; } = "DropOldest";
+    }
+}