Implement Google SSO One-Tap Pop-up

🔍 Problem Statement

Google SSO on Pelcro uses a redirect-based flow. The Google One-Tap pop-up (a less-friction sign-in method that appears automatically) is not implemented, which means users must click a button and go through a full redirect — increasing drop-off during registration.

💡 User Story

As a publisher, I want Google One-Tap sign-in pop-up integrated with Pelcro, so that returning users and new visitors can sign in with a single click without a full redirect flow.

🎯 Definition of Done (DoD)

A feature is done when:

✔️ Given a Pelcro-enabled site with Google SSO configured, when a visitor lands on the page, then the Google One-Tap pop-up appears (if eligible) — and clicking it authenticates the user and creates or links their Pelcro account.