fix: update QWEN_MODEL_ID default to 1.5B in main.py (missed in previous commit)

webapp/tipitaka-api/app/main.py

@@ -53,7 +53,7 @@ async def lifespan(app: FastAPI):
             qwen_runtime = os.getenv("QWEN_RUNTIME", "transformers")
             if qwen_runtime == "transformers":
                 from app.services.query_transform_service import QueryTransformService
-                model_id = os.getenv("QWEN_MODEL_ID", "Qwen/Qwen2.5-0.5B-Instruct")
+                model_id = os.getenv("QWEN_MODEL_ID", "Qwen/Qwen2.5-1.5B-Instruct")
                 logger.info(f"Pre-loading Qwen Model ({model_id}) for Query Transformation...")
                 await anyio.to_thread.run_sync(QueryTransformService.preload, model_id)
                 logger.info("Qwen Model preloaded.")