Replaces custom feed-row layout with the shared DataTable shell used
elsewhere in the app. Adds checkbox selection + bulk "Mark selected
read" toolbar alongside the existing "Mark all read". Uses DS
EmptyState for empty lists, severity-driven rowAccent for unread
tinting, and renderAlertExpanded for row detail.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
AlertRow is reused by AllAlertsPage and HistoryPage. Marking a row as read
happens when its link is followed (the detail sub-route will be added in
phase 10 polish). FIRING rows get an amber left border.
Adds 6 lazy-loaded route entries for the alerting UI (Inbox, All, History,
Rules list, Rule editor wizard, Silences) plus an `/alerts` → `/alerts/inbox`
redirect. Page components are placeholder stubs to be replaced in Phase 5/6/7.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
