Batch requests.

Currently we make a single request for each of them. We should use the batching feature that is available.
https://developers.google.com/resources/api-libraries/documentation/drive/v3/python/latest/index.html#new_batch_http_request

The issue references the Google Drive API v3 batch request feature. Look for code making individual Drive API calls, likely in upload or sync modules. Start by reading the linked Google API documentation to understand batch request structure. Then identify where sequential requests are made and refactor to use the batch HTTP request method. Test that the batch operation maintains the same functionality and error handling.

索引モデルが issue の本文から書いたものです。