handle client disconnects in SSE and streaming endpoints

Wrap SSE generators with BrokenPipeError/ConnectionResetError handling
so client disconnects during generation status polling, download progress,
or audio streaming don't produce unhandled Errno 32 errors.

Closes #248

backend/routes/generations.py

@@ -1,12 +1,15 @@
 """TTS generation endpoints."""
 
 import asyncio
+import logging
 import uuid
 
 from fastapi import APIRouter, Depends, HTTPException
 from fastapi.responses import StreamingResponse
 from sqlalchemy.orm import Session
 
+logger = logging.getLogger(__name__)
+
 from .. import models
 from ..services import history, profiles, tts
 from ..database import Generation as DBGeneration, VoiceProfile as DBVoiceProfile, get_db
@@ -181,6 +184,7 @@ async def get_generation_status(generation_id: str, db: Session = Depends(get_db
     import json
 
     async def event_stream():
+        try:
             while True:
                 db.expire_all()
                 gen = db.query(DBGeneration).filter_by(id=generation_id).first()
@@ -200,6 +204,8 @@ async def get_generation_status(generation_id: str, db: Session = Depends(get_db
                     return
 
                 await asyncio.sleep(1)
+        except (BrokenPipeError, ConnectionResetError, asyncio.CancelledError):
+            logger.debug("SSE client disconnected for generation %s", generation_id)
 
     return StreamingResponse(
         event_stream(),
@@ -265,9 +271,12 @@ async def stream_speech(
     wav_bytes = tts.audio_to_wav_bytes(audio, sample_rate)
 
     async def _wav_stream():
+        try:
             chunk_size = 64 * 1024
             for i in range(0, len(wav_bytes), chunk_size):
                 yield wav_bytes[i : i + chunk_size]
+        except (BrokenPipeError, ConnectionResetError, asyncio.CancelledError):
+            logger.debug("Client disconnected during audio stream")
 
     return StreamingResponse(
         _wav_stream(),

backend/utils/progress.py

@@ -246,6 +246,8 @@ class ProgressManager:
                     # Send heartbeat
                     yield ": heartbeat\n\n"
                     continue
+        except (BrokenPipeError, ConnectionResetError, asyncio.CancelledError):
+            logger.debug(f"SSE client disconnected from {model_name}")
         finally:
             # Remove from listeners
             if model_name in self._listeners: