大改，未验证

src/core/models.py

@@ -58,11 +58,49 @@ class WorkOrder(Base):
     # 关联处理过程记录
     process_history = relationship("WorkOrderProcessHistory", back_populates="work_order", order_by="WorkOrderProcessHistory.process_time")
 
+class ChatSession(Base):
+    """对话会话模型 — 将多轮对话组织为一个会话"""
+    __tablename__ = "chat_sessions"
+
+    id = Column(Integer, primary_key=True)
+    session_id = Column(String(100), unique=True, nullable=False)  # 唯一会话标识
+    user_id = Column(String(100), nullable=True)  # 用户标识
+    work_order_id = Column(Integer, ForeignKey("work_orders.id"), nullable=True)
+    title = Column(String(200), nullable=True)  # 会话标题（取首条消息摘要）
+    status = Column(String(20), default="active")  # active, ended
+    message_count = Column(Integer, default=0)  # 消息轮数
+    source = Column(String(50), nullable=True)  # 来源：websocket, api, feishu
+    ip_address = Column(String(45), nullable=True)
+    created_at = Column(DateTime, default=datetime.now)
+    updated_at = Column(DateTime, default=datetime.now, onupdate=datetime.now)
+    ended_at = Column(DateTime, nullable=True)
+
+    # 关联消息
+    messages = relationship("Conversation", back_populates="chat_session", order_by="Conversation.timestamp")
+
+    def to_dict(self):
+        return {
+            'id': self.id,
+            'session_id': self.session_id,
+            'user_id': self.user_id,
+            'work_order_id': self.work_order_id,
+            'title': self.title,
+            'status': self.status,
+            'message_count': self.message_count,
+            'source': self.source,
+            'ip_address': self.ip_address,
+            'created_at': self.created_at.isoformat() if self.created_at else None,
+            'updated_at': self.updated_at.isoformat() if self.updated_at else None,
+            'ended_at': self.ended_at.isoformat() if self.ended_at else None,
+        }
+
+
 class Conversation(Base):
     """对话记录模型"""
     __tablename__ = "conversations"
 
     id = Column(Integer, primary_key=True)
+    session_id = Column(String(100), ForeignKey("chat_sessions.session_id"), nullable=True)  # 关联会话
     work_order_id = Column(Integer, ForeignKey("work_orders.id"))
     user_message = Column(Text, nullable=False)
     assistant_response = Column(Text, nullable=False)
@@ -79,6 +117,7 @@ class Conversation(Base):
     cpu_usage = Column(Float)  # CPU使用率
 
     work_order = relationship("WorkOrder", back_populates="conversations")
+    chat_session = relationship("ChatSession", back_populates="messages")
 
 class KnowledgeEntry(Base):
     """知识库条目模型"""