sync from GitHub 1362c47: feat: update version code and enhance backup system

app/api/user_backups_v6.py

@@ -354,7 +354,9 @@ async def download_blob(key: str, request: Request):
         raise _err("unauthorized", "missing user", status=401)
     if not _is_sha256_hex(key):
         raise _err("invalid_key", "key 必须是 64 位 sha256 hex", status=400)
-    blob_path = backup_v6_store.get_blob_local_path(key)
+    # get_blob_local_path 本地缺失时会同步走 Hub 回源（网络 IO），
+    # 必须放 to_thread，否则阻塞事件循环拖垮整个服务
+    blob_path = await asyncio.to_thread(backup_v6_store.get_blob_local_path, key)
     if not blob_path or not blob_path.exists():
         raise _err("blob_not_found", "blob 不存在", status=404)
     meta = backup_v6_store.get_blob_meta(key)