feat: 更新 Server 后端服务

- 更新 agent handler 和 service 层
- 新增 chat_group handler 和 service
- 删除废弃的 chat_handler
- 更新 tool 相关处理
- 更新 API 文档和依赖

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

server/internal/service/agent_service.go

@@ -115,7 +115,7 @@ func (s *AgentService) Chat(req AgentChatRequest) (*AgentChatResponse, error) {
 	log.Printf("[AgentService] Sending to Python: model_id=%s, api_key=%s, base_url=%s, provider=%s, model=%s",
 		req.ModelID, apiKeyPreview, req.BaseURL, req.ModelProvider, req.ModelName)
 
-	url := fmt.Sprintf("%s/agent/chat", s.pythonURL)
+	url := fmt.Sprintf("%s/api/v1/agent/chat", s.pythonURL)
 
 	jsonData, err := json.Marshal(req)
 	if err != nil {
@@ -153,7 +153,7 @@ func (s *AgentService) Chat(req AgentChatRequest) (*AgentChatResponse, error) {
 
 // TeamChat 多智能体群聊
 func (s *AgentService) TeamChat(req TeamChatRequest) (*TeamChatResponse, error) {
-	url := fmt.Sprintf("%s/agent/team/chat", s.pythonURL)
+	url := fmt.Sprintf("%s/api/v1/agent/team/chat", s.pythonURL)
 
 	// 设置默认策略
 	if req.Strategy == "" {
@@ -228,7 +228,7 @@ func (s *AgentService) ChatStream(c interface{}, agentID int, message, sessionID
 		log.Printf("[ChatStream] modelID is empty or modelRepo is nil: modelID=%s, modelRepo=%v", modelID, s.modelRepo != nil)
 	}
 
-	streamURL := fmt.Sprintf("%s/agent/chat/stream", s.pythonURL)
+	streamURL := fmt.Sprintf("%s/api/v1/agent/chat/stream", s.pythonURL)
 
 	jsonData, err := json.Marshal(reqBody)
 	if err != nil {