Improve deployment safety and chat reliability

backend/app/routers/voice.py

@@ -7,7 +7,7 @@ from fastapi.responses import Response
 from app.auth import require_admin, get_current_user
 from app.config import get_settings
 from app.models import User
-from app.schemas import VoiceConfigOut, VoiceInstructionRequest
+from app.schemas import SynthesizeRequest, VoiceConfigOut, VoiceInstructionRequest
 from app.services.llm_service import summarize_instruction
 from app.services.voice_service import synthesize, transcribe
 
@@ -48,12 +48,12 @@ async def transcribe_audio(
 
 @router.post("/synthesize")
 async def synthesize_text(
-    text: str,
+    body: SynthesizeRequest,
     user: User = Depends(get_current_user),
 ):
     """Convert text to speech audio (API mode only)."""
     try:
-        audio_bytes = await synthesize(text)
+        audio_bytes = await synthesize(body.text)
         return Response(content=audio_bytes, media_type="audio/mpeg")
     except Exception as e:
         logger.error(f"Synthesis failed: {str(e)}", exc_info=True)