fix: detect rate-limit error, auto-retry once after 30s with friendly message

fix: remove cron, fix new-user flow (ensureShellularRunning on every login)

feat: keep-alive card with live status, dot indicator, ping-now button

feat: first-time setup panel with copy buttons for shellular secrets

fix: render QR via qrcode.js canvas instead of broken ASCII art

revert: clean state, no retry spam

fix: auto-retry with 60s backoff on rate-limit, expose /api/shellular/credentials

fix: pin machine-id + seed shellular config from env vars to bypass rate limit

Initial upload: Shellular Web UI + keep-alive service