feat: Phase 5 STT — DashScope Gummy 实时语音识别 + 本地 Whisper 回退

- DashScope WebSocket STT 客户端 (gummy-chat-v1)
- 双引擎架构: DashScope 优先, Whisper 本地回退
- 实时流式 STT WebSocket 端点
- DevTools 模型搜索框焦点修复

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

backend/voice-service/internal/handler/streaming_stt.go

@@ -0,0 +1,118 @@
+package handler
+
+import (
+	"encoding/json"
+	"net/http"
+	"sync"
+	"time"
+
+	"github.com/gorilla/websocket"
+
+	"github.com/yourname/cyrene-ai/pkg/logger"
+	"github.com/yourname/cyrene-ai/voice-service/internal/service"
+)
+
+var upgrader = websocket.Upgrader{
+	ReadBufferSize:  4096,
+	WriteBufferSize: 4096,
+	CheckOrigin: func(r *http.Request) bool {
+		return true
+	},
+}
+
+// StreamingSTTHandler 处理实时语音识别 WebSocket 连接。
+// 客户端通过 WebSocket 流式发送音频二进制帧，服务端逐帧转发到 DashScope，
+// 将识别结果通过 WebSocket JSON 消息返回。
+type StreamingSTTHandler struct {
+	svc *service.STTService
+}
+
+// NewStreamingSTTHandler 创建流式 STT 处理器。
+func NewStreamingSTTHandler(svc *service.STTService) *StreamingSTTHandler {
+	return &StreamingSTTHandler{svc: svc}
+}
+
+// HandleStreamingSTT 处理 WebSocket 升级和实时 STT 会话。
+// GET /api/v1/stt/stream
+func (h *StreamingSTTHandler) HandleStreamingSTT(w http.ResponseWriter, r *http.Request) {
+	if !h.svc.IsAvailable() {
+		writeJSON(w, http.StatusServiceUnavailable, map[string]interface{}{
+			"error": "STT 引擎不可用",
+		})
+		return
+	}
+
+	language := r.URL.Query().Get("language")
+	if language == "" {
+		language = "zh"
+	}
+
+	conn, err := upgrader.Upgrade(w, r, nil)
+	if err != nil {
+		logger.Printf("[stream-stt] WebSocket 升级失败: %v", err)
+		return
+	}
+	defer conn.Close()
+
+	logger.Printf("[stream-stt] 客户端已连接")
+
+	var mu sync.Mutex
+	conn.SetWriteDeadline(time.Now().Add(60 * time.Second))
+
+	// 读取音频帧并发送到 DashScope
+	for {
+		msgType, data, err := conn.ReadMessage()
+		if err != nil {
+			if websocket.IsUnexpectedCloseError(err, websocket.CloseGoingAway, websocket.CloseNormalClosure) {
+				logger.Printf("[stream-stt] 读取错误: %v", err)
+			}
+			break
+		}
+
+		// 支持文本控制消息
+		if msgType == websocket.TextMessage {
+			var ctrl map[string]interface{}
+			if json.Unmarshal(data, &ctrl) == nil {
+				if ctrl["action"] == "stop" {
+					mu.Lock()
+					conn.WriteJSON(map[string]interface{}{
+						"type":   "done",
+						"action": "stop",
+					})
+					mu.Unlock()
+					break
+				}
+			}
+			continue
+		}
+
+		// 二进制音频帧：进行识别
+		if msgType == websocket.BinaryMessage {
+			format := r.URL.Query().Get("format")
+			if format == "" {
+				format = "pcm"
+			}
+
+			text, err := h.svc.Transcribe(data, format, language)
+			mu.Lock()
+			if err != nil {
+				conn.WriteJSON(map[string]interface{}{
+					"type":  "error",
+					"error": err.Error(),
+				})
+			} else if text != "" {
+				conn.WriteJSON(map[string]interface{}{
+					"type": "result",
+					"text": text,
+					"final": true,
+				})
+			}
+			mu.Unlock()
+		}
+	}
+}
+
+// RegisterStreamingRoutes 注册流式 STT 路由。
+func (h *StreamingSTTHandler) RegisterStreamingRoutes(mux *http.ServeMux) {
+	mux.HandleFunc("/api/v1/stt/stream", h.HandleStreamingSTT)
+}