实现消息记录功能，包括增删改查和标记已读，优化消息列表展示和未读消息计数

Entity/MessageRecord.cs

@@ -0,0 +1,22 @@
+namespace Entity;
+
+/// <summary>
+/// 消息实体
+/// </summary>
+public class MessageRecord : BaseEntity
+{
+    /// <summary>
+    /// 消息标题
+    /// </summary>
+    public string Title { get; set; } = string.Empty;
+
+    /// <summary>
+    /// 消息内容
+    /// </summary>
+    public string Content { get; set; } = string.Empty;
+
+    /// <summary>
+    /// 是否已读
+    /// </summary>
+    public bool IsRead { get; set; } = false;
+}