feat(analytics): Umami integration with per-port admin settings

Adds /[portSlug]/website-analytics dashboard page (pageviews, top
pages, top referrers) and a per-port admin config UI for the
Umami URL / website-ID / API token. Settings live in system_settings
keyed per-port so a future second port has its own Umami account.
Adds a website glance tile to the main dashboard, a server-side
test-credentials endpoint, and a stable cache key for the active-
visitor poll so React Query doesn't fragment the cache per range.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

src/app/(dashboard)/[portSlug]/website-analytics/page.tsx

@@ -0,0 +1,11 @@
+import type { Metadata } from 'next';
+
+import { WebsiteAnalyticsShell } from '@/components/website-analytics/website-analytics-shell';
+
+export const metadata: Metadata = {
+  title: 'Website analytics',
+};
+
+export default function WebsiteAnalyticsPage() {
+  return <WebsiteAnalyticsShell />;
+}