fix: 豆包API加model_type=4指定ICL 2.0 + 优化音频参数

之前缺少model_type参数可能回退到ICL 1.0导致音质不如平台调试

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

backend/app/services/doubao_service.py

@@ -1,6 +1,8 @@
 import os
 import uuid
 import requests
+import base64
+
 
 def synthesize_doubao(text, speed=1.0, pitch=0, volume=1.0, emotion='neutral'):
     """调用火山引擎豆包 Seed-ICL 2.0 语音合成 API"""
@@ -11,7 +13,8 @@ def synthesize_doubao(text, speed=1.0, pitch=0, volume=1.0, emotion='neutral'):
     url = 'https://openspeech.bytedance.com/api/v1/tts'
     headers = {
         'x-api-key': api_key,
-        'Content-Type': 'application/json'
+        'Content-Type': 'application/json',
+        'X-Api-Resource-Id': 'seed-icl-2.0'
     }
 
     payload = {
@@ -25,11 +28,13 @@ def synthesize_doubao(text, speed=1.0, pitch=0, volume=1.0, emotion='neutral'):
             'voice_type': 'S_LK0j18H72',
             'encoding': 'mp3',
             'speed_ratio': speed,
+            'bitrate': 128000,
         },
         'request': {
             'reqid': str(uuid.uuid4()),
             'text': text,
-            'operation': 'query'
+            'operation': 'query',
+            'model_type': 4,  # ICL 2.0 模型
         }
     }
 
@@ -42,7 +47,6 @@ def synthesize_doubao(text, speed=1.0, pitch=0, volume=1.0, emotion='neutral'):
 
     # 豆包返回格式: {"code": 3000, "data": "base64编码的音频"}
     if result.get('code') == 3000 and result.get('data'):
-        import base64
         audio_bytes = base64.b64decode(result['data'])
         return audio_bytes