chore: 同步 .env.example — 新增 DashScope STT、微服务地址、离线思考间隔等缺失配置

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

backend/.env.example

@@ -20,7 +20,12 @@ LLM_API_KEY=sk-xxxxx
 LLM_MODEL=gpt-4o
 LLM_FALLBACK_MODEL=gpt-4o-mini
 
-# ========== TTS/ASR ==========
+# ========== DashScope STT (语音识别) ==========
+DASHSCOPE_API_KEY=sk-xxxxx
+DASHSCOPE_STT_MODEL=qwen3-asr-flash-2026-02-10
+DASHSCOPE_STT_REALTIME_MODEL=qwen3-asr-flash-realtime
+
+# ========== TTS/ASR (本地回退) ==========
 TTS_PROVIDER=edge-tts
 TTS_VOICE=zh-CN-XiaoxiaoNeural
 ASR_PROVIDER=faster-whisper
@@ -46,19 +51,20 @@ REGISTRATION_ENABLED=true
 JWT_SECRET=your-secret-key-change-in-production
 JWT_EXPIRY_HOURS=720
 
-# ========== JWT ==========
-JWT_SECRET=your-secret-key-change-in-production
-JWT_EXPIRY_HOURS=720
-
 # ========== 内部服务认证 ==========
 INTERNAL_SERVICE_TOKEN=your-internal-token-change-in-production
 
 # ========== IoT 调试服务 ==========
-# 优先使用 IOT_SERVICE_URL，如果不存在则回退到 IOT_DEBUG_SERVICE_URL（向后兼容）
 IOT_SERVICE_URL=http://localhost:8083
 
+# ========== 后端微服务地址 ==========
+MEMORY_SERVICE_URL=http://localhost:8091
+TOOL_ENGINE_URL=http://localhost:8092
+VOICE_SERVICE_URL=http://localhost:8093
+
 # ========== 后台思考 ==========
 ENABLE_BACKGROUND_THINKING=true
+THINK_OFFLINE_GAP_SEC=600
 
 # ========== Webhook (第三方平台接入) ==========
 WEBHOOK_API_KEY=your-webhook-api-key