Adds 3 fields to mail_connections so UI can distinguish between
"connection alive but no new mail" vs "connection dead" vs "auth-failed":
- last_connect_error — text of last IMAP error (auth-fail, connect-fail)
- last_connect_error_at — timestamp of error
- last_idle_heartbeat_at — updated every 2min by NOOP-success in daemon
Daemon (backend/imap-idle/index.mjs):
- updateConnectionError() / clearConnectionError() / updateIdleHeartbeat()
SQL helpers
- logError now uses err.responseText (shows "AUTHENTICATIONFAILED" instead
of generic "Command failed")
- clearError on connect() success
- updateError on connect() catch
- updateHeartbeat in NOOP-success-path (every 2min)
API (status.get.ts): returns the 3 new fields per account.
Migration: ALTER TABLE rebreak.mail_connections ADD COLUMN ... (idempotent).
UI-side (in flight, separate task): MailAccountCard renders auth-error
banner when lastConnectError != null + heartbeat-based "live" indicator.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
