CVE-2026-59219: Open WebUI: Realtime endpoints accept Redis-revoked JWTs after signout/backchannel logout

With Redis configured, Open WebUI supports JWT revocation: POST /api/v1/auths/signout (per-token jti) and OIDC back-channel logout (per-user revoked_at) record revocations in Redis, and HTTP auth (get_current_user) rejects revoked tokens with 401. The realtime authentication surfaces do not perform this check: Socket.IO connect / user-join / join-channels / join-note and the terminal websocket first-message auth validate tokens with decode_token() only (signature + expiry). A JWT revoked by sign-out or back-channel logout therefore continues to authenticate new realtime connections, even though the same token is rejected on HTTP.