Step 12：后端轻量优化（API 稳定性 & 前端友好）

backend/app/utils/pagination.py

@@ -0,0 +1,7 @@
+from collections.abc import Iterable
+from typing import Any
+
+
+def paginate(items: Iterable[Any], total: int | None = None) -> dict[str, Any]:
+    items_list = list(items)
+    return {"items": items_list, "total": total if total is not None else len(items_list)}