openai/gpt-chat-latest → A (3:2)

Side A introduces a shared `util/get-base-url` used across multiple OAuth/login modules, replacing inconsistent hardcoded hostnames and environment checks with `HOSTNAME`/origin-aware logic, which fixes redirect and callback behavior for custom deployments. It also updates the deployment workflow for the staging branch. Side B improves the auth UX by returning HTML fragments for inline form updates instead of redirects, but its impact is narrower and primarily affects interaction flow rather than deployment correctness or cross-environment reliability.