Fix Piper 1.2+ synthesize API: pass wav_file BytesIO buffer

main.py

@@ -90,9 +90,9 @@ async def tts(request: TTSRequest):
         raise HTTPException(400, f"Voice load failed: {str(e)}")
     
     try:
-        audio = voice.synthesize(request.text, speaker_id=request.speaker_id)
         buffer = BytesIO()
-        sf.write(buffer, audio, request.sample_rate, format='WAV')
+        # Piper 1.2+ requires wav_file parameter
+        voice.synthesize(request.text, speaker_id=request.speaker_id, wav_file=buffer)
         buffer.seek(0)
         return Response(
             content=buffer.read(),
@@ -113,4 +113,4 @@ async def root():
         "available_voices": list(VOICE_MODELS.keys()),
         "endpoint": "/tts (POST)",
         "example": {"text": "你好，这是 Piper TTS 测试", "lang": "zh"}
-    }
+    }