feat: Phase 5.1 - Client 扩展，添加 orchestrator 依赖

- 扩展 Client 结构体，添加 sessionManager、orchestrator、cancelFuncs 字段
- 创建 WSClient 适配器实现 orchestrator.Sender 接口
- 更新 ServeWS 函数签名，接收 orchestrator 参数
- 在 main.go 中初始化 AI 服务和 Orchestrator

backend/internal/ws/handler.go

@@ -13,6 +13,7 @@ import (
 	"github.com/hhs/camtalk/internal/errors"
 	"github.com/hhs/camtalk/internal/logger"
 	"github.com/hhs/camtalk/internal/models"
+	"github.com/hhs/camtalk/internal/orchestrator"
 	"github.com/hhs/camtalk/internal/session"
 )
 
@@ -22,9 +23,12 @@ var upgrader = websocket.Upgrader{
 
 // Client 代表一个 WebSocket 客户端连接。
 type Client struct {
-	conn      *websocket.Conn
-	sessionID string
-	mu        sync.Mutex
+	conn          *websocket.Conn
+	sessionID     string
+	sessionMgr    session.Manager
+	orchestrator  orchestrator.Orchestrator
+	cancelFuncs   map[string]context.CancelFunc // requestID → cancel func
+	mu            sync.Mutex
 }
 
 // SendJSON 向客户端发送 JSON 消息（公开以便 errors 包调用）。
@@ -34,14 +38,50 @@ func (c *Client) SendJSON(v any) error {
 	return c.conn.WriteJSON(v)
 }
 
+// WSClient 实现 orchestrator.Sender 接口，将消息推送到 WebSocket 连接。
+type WSClient struct {
+	client    *Client
+	requestID string
+}
+
+// SendSTTResult 发送语音识别结果。
+func (w *WSClient) SendSTTResult(result models.WsSTTResult) error {
+	result.RequestID = w.requestID
+	return w.client.SendJSON(result)
+}
+
+// SendLLMChunk 发送 LLM 流式文本增量。
+func (w *WSClient) SendLLMChunk(chunk models.WsLLMChunk) error {
+	chunk.RequestID = w.requestID
+	return w.client.SendJSON(chunk)
+}
+
+// SendLLMDone 发送 LLM 流结束信号。
+func (w *WSClient) SendLLMDone(done models.WsLLMDone) error {
+	done.RequestID = w.requestID
+	return w.client.SendJSON(done)
+}
+
+// SendTTSAudio 发送 TTS 音频数据。
+func (w *WSClient) SendTTSAudio(audio models.WsTTSAudio) error {
+	audio.RequestID = w.requestID
+	return w.client.SendJSON(audio)
+}
+
+// SendError 发送错误消息。
+func (w *WSClient) SendError(err models.WsError) error {
+	err.RequestID = w.requestID
+	return w.client.SendJSON(err)
+}
+
 // ServeWS 处理 WebSocket 升级请求。
-func ServeWS(sessionMgr session.Manager) gin.HandlerFunc {
+func ServeWS(sessionMgr session.Manager, orch orchestrator.Orchestrator) gin.HandlerFunc {
 	return func(c *gin.Context) {
-		serveWS(c, sessionMgr)
+		serveWS(c, sessionMgr, orch)
 	}
 }
 
-func serveWS(c *gin.Context, sessionMgr session.Manager) {
+func serveWS(c *gin.Context, sessionMgr session.Manager, orch orchestrator.Orchestrator) {
 	conn, err := upgrader.Upgrade(c.Writer, c.Request, nil)
 	if err != nil {
 		logger.Log.Errorw("websocket upgrade failed", "error", err)
@@ -56,7 +96,13 @@ func serveWS(c *gin.Context, sessionMgr session.Manager) {
 		return
 	}
 
-	client := &Client{conn: conn, sessionID: sessionID}
+	client := &Client{
+		conn:         conn,
+		sessionID:    sessionID,
+		sessionMgr:   sessionMgr,
+		orchestrator: orch,
+		cancelFuncs:  make(map[string]context.CancelFunc),
+	}
 
 	// 发送 connected 消息
 	_ = client.SendJSON(models.WsConnected{