Add sac_users table, JWT roles, settings/users API guarded for admin, Users page in UI, and sac_manage_user.py CLI.
Co-authored-by: Cursor <cursoragent@cursor.com>
Centralize APP_VERSION 0.2.0; /health and /healthz return version;
startup log line; UI title Security Alert Center v.0.2.0;
SSE /api/v1/stream/events for live dashboard counters.