Switch deploy_playstore.py from requests/AuthorizedSession to the
googleapiclient.discovery client with google-auth-httplib2, so that
AuthorizedHttp(timeout=300) enforces a hard socket timeout on all
requests and num_retries=3 on every .execute() call enables automatic
retries for transient failures.
Update flake.nix and ci/main.go to install the new dependencies
(google-api-python-client, google-auth-httplib2, httplib2) instead of
the old google-auth + requests pair.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
