chore: 整理项目结构，清理归档文件，更新部署配置

backend/app/models/message.py

@@ -10,7 +10,7 @@ import uuid
 from datetime import datetime, timedelta
 from typing import Any, Dict, Optional
 
-from sqlalchemy import Boolean, DateTime, ForeignKey, Index, Integer, JSON, String, Text
+from sqlalchemy import BigInteger, Boolean, DateTime, ForeignKey, Index, Integer, JSON, String, Text
 from sqlalchemy.orm import Mapped, mapped_column
 
 from app.database import Base
@@ -232,6 +232,15 @@ class Message(Base):
         comment="创建时间",
     )
 
+    # 服务端时间戳（毫秒级）
+    # 由后端在接收企微回调/创建消息时写入 int(time.time() * 1000)
+    server_timestamp: Mapped[Optional[int]] = mapped_column(
+        BigInteger,
+        nullable=True,
+        default=None,
+        comment="服务端时间戳(毫秒)",
+    )
+
     # --------------------------------------------------------------------------
     # 索引定义（和架构文档 DDL 严格一致）
     # --------------------------------------------------------------------------