Add ValidateAdmin endpoint that checks JWT admin claim for use as an
nginx auth_request subrequest. Widen cookie path from backend endpoint
to "/" so the access_token is sent on all paths. Extend access token
lifetime from 24h to 7 days. Disable hasura service by default via
Docker profile.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>