feat: Agent 服务日志功能和后端更新

- agent/main.py: 添加日志记录功能
- agent/llm: 更新 anthropic, openai, factory
- agent/core/agent.py: 更新
- server: agent_handler, agent_service, chat_service 更新

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

server/internal/handler/agent_handler.go

@@ -25,6 +25,7 @@ type ChatRequest struct {
 	AgentID   int    `json:"agent_id" binding:"required"`
 	Message   string `json:"message" binding:"required"`
 	SessionID string `json:"session_id"`
+	ModelID   string `json:"model_id"`
 }
 
 // ChatResponse 对话响应
@@ -54,6 +55,7 @@ func (h *AgentHandler) Chat(c *gin.Context) {
 		Message:   req.Message,
 		UserID:    userID,
 		SessionID: req.SessionID,
+		ModelID:   req.ModelID,
 	}
 
 	result, err := h.agentService.Chat(pythonReq)