feat(ui/alerts): AllAlertsPage + HistoryPage

AllAlertsPage: state filter chips (Open/Firing/Acked/All).
HistoryPage: RESOLVED filter, respects retention window.

ui/src/pages/Alerts/HistoryPage.tsx

@@ -1,3 +1,27 @@
+import { SectionHeader } from '@cameleer/design-system';
+import { PageLoader } from '../../components/PageLoader';
+import { useAlerts } from '../../api/queries/alerts';
+import { AlertRow } from './AlertRow';
+import css from './alerts-page.module.css';
+
 export default function HistoryPage() {
-  return <div>HistoryPage — coming soon</div>;
+  const { data, isLoading, error } = useAlerts({ state: 'RESOLVED', limit: 200 });
+
+  if (isLoading) return <PageLoader />;
+  if (error) return <div className={css.page}>Failed to load history: {String(error)}</div>;
+
+  const rows = data ?? [];
+
+  return (
+    <div className={css.page}>
+      <div className={css.toolbar}>
+        <SectionHeader>History</SectionHeader>
+      </div>
+      {rows.length === 0 ? (
+        <div className={css.empty}>No resolved alerts in retention window.</div>
+      ) : (
+        rows.map((a) => <AlertRow key={a.id} alert={a} unread={false} />)
+      )}
+    </div>
+  );
 }