- Add codexAuthFile.ts utility: builds Codex auth.json payload from OAuth connection
(id_token, access_token, refresh_token, account_id) with auto-refresh if expired
- Add POST /api/providers/[id]/codex-auth/export: downloads auth.json file
- Add POST /api/providers/[id]/codex-auth/apply-local: writes auth.json to local CLI path
- Add 'Apply auth' and 'Export auth' buttons to ConnectionRow (Codex provider only)
- Add i18n keys for en and pt-BR
