The server-to-server token exchange was hitting the external URL
(https://account.rose-ash.com/...) which can fail from inside Docker
due to DNS/hairpin NAT. Now uses INTERNAL_URL_ACCOUNT (already set in
both docker-compose files) for the POST. Adds logging at all three
failure points so silent redirects are diagnosable.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
Existing sessions have email=None since the field was just added.
Username IS the email in Art-DAG (OAuth returns user.email as username).
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>