feat: add admin links management and updaterup page

- Implemented AdminLinksPage for managing link entries with admin role check.
- Created API routes for fetching, updating, and deleting link entries.
- Added ProductTabs component for navigation between Backerup and Updaterup.
- Developed UpdaterupPage with detailed features, setup instructions, and statistics.
- Introduced links database functionality for runtime-editable link overrides.

frontend/app/admin/links/page.tsx

@@ -0,0 +1,20 @@
+import type { Metadata } from 'next'
+import { redirect } from 'next/navigation'
+import { getSession } from '@/lib/session'
+import { getAllLinkEntries } from '@/lib/links-db'
+import LinksClient from '../LinksClient'
+
+export const metadata: Metadata = {
+  title: 'Admin — Links — Backerup',
+}
+
+export default async function AdminLinksPage() {
+  const session = await getSession()
+  if (!session || session.role !== 'admin') {
+    redirect('/')
+  }
+
+  const entries = await getAllLinkEntries()
+
+  return <LinksClient initialEntries={entries} />
+}