Register Local Network's Google client for YouTube uploads #293

Create a Google Cloud desktop OAuth client with the YouTube Data API enabled. Set GOOGLE_CLIENT_ID and GOOGLE_CLIENT_SECRET on the website's service, and replace the placeholder client_id in plugins/youtube/locallibrary-plugin.toml. Submit the consent screen for verification of the youtube.upload scope before more than 100 people sign in; while it's in Testing, refresh tokens expire after 7 days. Then publish one set with --to youtube:video, and check that the 15-minute limit for unverified channels and the shared daily upload quota read the way the docs say. Part of #287.