- Add bgalert package: classify provider errors (auth, billing,
model_not_found), store alert in system_configs, broadcast WS event
- Wire AlertDeps into consolidation (episodic, semantic, dreaming)
and vault enrich workers to report failures after retry exhaustion
- Auto-clear alert when admin changes provider-related system configs
- Add BackgroundErrorBanner component with dismiss + "Fix in Settings"
- Lift settings modal state to AppLayout so banner can open it
- Add EventBackgroundError to admin-only WS event filter
- Add i18n translations (en/vi/zh) for alert messages and reasons
