Store SSE OBO refresh-token recovery bridges in MongoDB instead of
process-local memory so /api/auth/refresh can recover after worker
restarts or cross-worker routing.
Derive bridge expiry from REFRESH_TOKEN_EXPIRY so the recovery window
matches the stale refreshToken cookie it repairs, and delete bridges
after successful recovery.
When an inline OBO refresh rotates the OpenID refresh token after SSE headers
have already been sent, the browser refreshToken cookie cannot be updated. Store
a short-lived encrypted bridge from the stale cookie token to the rotated token
so /api/auth/refresh can recover after express-session loss.
Use the signed openid_user_id cookie to load user context for bridge validation,
retry only on invalid_grant, and delete the bridge only after the bridged refresh
succeeds.
