feat(activity-log): phase 6 - dashboard widget + settings panel + docs
- Dashboard 'Recent Activity' widget: latest 5 entries, live prepend, 'View all' -> Activity tab
- Settings 'Activity Log' panel: retention (enabled/max_days/max_entries) GET/PUT, clear (confirm + auth-required toast), CSV/JSON export
- audit-log vs ephemeral debug Log Viewer distinction note + cross-links
- public helpers fetchRecentEntries/renderCompactEntry on activity-log.ts (reused, no dup markup)
- README Activity Log section; i18n across en/ru/zh
- review fixes: clear 401 surfaces toast; empty widget transitions on first live event
alexei.dolgolyov
6e1dd2111d