fix: faster sac-api restart (TimeoutStopSec, SSE cancel on shutdown)

backend/app/api/v1/stream.py

@@ -53,14 +53,17 @@ def _dashboard_snapshot(db: Session) -> dict:
 
 
 async def _sse_generator():
-    while True:
-        db = SessionLocal()
-        try:
-            payload = _dashboard_snapshot(db)
-        finally:
-            db.close()
-        yield f"data: {json.dumps(payload, ensure_ascii=False)}\n\n"
-        await asyncio.sleep(SSE_INTERVAL_SEC)
+    try:
+        while True:
+            db = SessionLocal()
+            try:
+                payload = _dashboard_snapshot(db)
+            finally:
+                db.close()
+            yield f"data: {json.dumps(payload, ensure_ascii=False)}\n\n"
+            await asyncio.sleep(SSE_INTERVAL_SEC)
+    except asyncio.CancelledError:
+        return
 
 
 def _sse_auth(token: str = Query(..., description="JWT access_token")) -> str: