调整数据库结构，实现消息模板管理

Atomx.Common/Entities/MessageTemplate.cs

@@ -16,6 +16,11 @@ namespace Atomx.Common.Entities
         [Key]
         public long Id { get; set; }
 
+        /// <summary>
+        /// 站点ID
+        /// </summary>
+        public long SiteId { get; set; }
+
         /// <summary>
         /// 语言编码
         /// </summary>
@@ -50,6 +55,12 @@ namespace Atomx.Common.Entities
         [Column(TypeName = "text")]
         public string Body { get; set; } = string.Empty;
 
+        /// <summary>
+        /// 附件文件地址列表，多个附件以逗号分隔
+        /// </summary>
+        [Column(TypeName = "varchar(1024)")]
+        public string Attachments { get; set; } = string.Empty;
+
         /// <summary>
         /// 是否可用
         /// </summary>