Public callback for Google app login

Google app login establishes an Account application session. It does not authorize Gmail mailbox access. For a local HTTPS application, the deployment's public tunnel forwards the supported callback to Account. See Google Cloud setup and account login setup.

In Google Auth Platform Clients, register the exact callback for the app-login Web client. Mailbox OAuth uses a separate Web client and return path. Keep their credentials separate.

After the callback, the browser returns to the Account/BFF origin that started the flow. Another developer's tunnel, an incorrect port, or a mismatched redirect URI can prevent login. Correct the registered deployment URL before starting a fresh login attempt.