Implement smart multi-speaker TTS detection

- Only activate multi-speaker TTS when multiSpeakerVoiceConfig is present
- Preserve original TTS functionality for single-speaker requests
- Support dynamic model selection from user request
- Add fallback mechanism to standard service if multi-speaker TTS fails
- Maintain full backward compatibility with existing TTS systems

app/router/gemini_routes.py

@@ -113,24 +113,34 @@ async def generate_content(
         logger.info(f"Handling Gemini content generation request for model: {model_name}")
         logger.debug(f"Request: \n{request.model_dump_json(indent=2)}")
 
+        # 检测是否为多人TTS请求
+        is_multi_speaker_tts = False
+        if "tts" in model_name.lower():
+            try:
+                raw_body = await raw_request.body()
+                raw_data = json.loads(raw_body.decode('utf-8'))
+
+                # 检查是否包含多人语音配置
+                speech_config = raw_data.get("generationConfig", {}).get("speechConfig", {})
+                if "multiSpeakerVoiceConfig" in speech_config:
+                    is_multi_speaker_tts = True
+                    logger.info("Detected multi-speaker TTS request")
+                    logger.info(f"Raw request data for multi-speaker TTS: {json.dumps(raw_data, indent=2, ensure_ascii=False)}")
+
+                    # 将TTS字段添加到请求对象中
+                    setattr(request, '_raw_tts_data', raw_data)
+            except Exception as e:
+                logger.warning(f"Failed to parse request for multi-speaker TTS detection: {e}")
+
         logger.info(f"Using API key: {api_key}")
 
         if not await model_service.check_model_support(model_name):
             raise HTTPException(status_code=400, detail=f"Model {model_name} is not supported")
 
-        # 检测是否为TTS模型，如果是则使用TTS服务
-        if "tts" in model_name.lower():
-            logger.info("Detected TTS model, using TTS-enhanced service")
+        # 只有多人TTS请求才使用增强服务
+        if is_multi_speaker_tts:
             try:
-                # 从原始请求体中提取TTS字段
-                raw_body = await raw_request.body()
-                raw_data = json.loads(raw_body.decode('utf-8'))
-                logger.info(f"Raw request data for TTS: {json.dumps(raw_data, indent=2, ensure_ascii=False)}")
-
-                # 将TTS字段添加到请求对象中
-                setattr(request, '_raw_tts_data', raw_data)
-
-                # 使用TTS增强服务
+                logger.info("Using multi-speaker TTS enhanced service")
                 tts_service = await get_tts_chat_service(key_manager)
                 response = await tts_service.generate_content(
                     model=model_name,
@@ -139,10 +149,9 @@ async def generate_content(
                 )
                 return response
             except Exception as e:
-                logger.warning(f"TTS processing failed, falling back to standard service: {e}")
-                # 如果TTS处理失败，回退到标准服务
+                logger.warning(f"Multi-speaker TTS processing failed, falling back to standard service: {e}")
 
-        # 使用标准服务处理非TTS模型或TTS失败的情况
+        # 使用标准服务处理所有其他请求（包括单人TTS）
         response = await chat_service.generate_content(
             model=model_name,
             request=request,