Operators can now set who receives the daily digest and the real-time alerts
from the dashboard (Security Scan -> Notifikasi) instead of editing .env:

- Livewire settings page: digest recipients, send time, enable/disable, send
  even when empty; extra alert recipients; 'Kirim Uji' button to send the
  digest immediately and prove the setup.
- Values persist in nawasara_settings (Setting::get/set), read by the digest
  job, the schedule, and the alerting resolver, each falling back to env/config
  so an untouched deployment is unchanged.
- New permission secscan.settings.manage + route + sidebar entry.

Requires nawasara/core (Setting) — already an implicit dependency via the app.