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/api/admin/links/[key]/route.ts

@@ -0,0 +1,22 @@
+import { NextResponse } from 'next/server'
+import { getSession } from '@/lib/session'
+import { resetLink, type LinkKey } from '@/lib/links-db'
+import { LINKS } from '@/lib/links'
+
+export async function DELETE(
+  _request: Request,
+  { params }: { params: Promise<{ key: string }> },
+) {
+  const session = await getSession()
+  if (!session || session.role !== 'admin') {
+    return NextResponse.json({ error: 'Forbidden' }, { status: 403 })
+  }
+
+  const { key } = await params
+  if (!(key in LINKS)) {
+    return NextResponse.json({ error: 'Unknown link key' }, { status: 400 })
+  }
+
+  await resetLink(key as LinkKey)
+  return NextResponse.json({ ok: true })
+}

frontend/app/api/admin/links/route.ts

@@ -0,0 +1,40 @@
+import { NextResponse } from 'next/server'
+import { getSession } from '@/lib/session'
+import { getAllLinkEntries, setLink, type LinkKey } from '@/lib/links-db'
+import { LINKS } from '@/lib/links'
+
+export async function GET() {
+  const session = await getSession()
+  if (!session || session.role !== 'admin') {
+    return NextResponse.json({ error: 'Forbidden' }, { status: 403 })
+  }
+  const entries = await getAllLinkEntries()
+  return NextResponse.json(entries)
+}
+
+export async function PUT(request: Request) {
+  const session = await getSession()
+  if (!session || session.role !== 'admin') {
+    return NextResponse.json({ error: 'Forbidden' }, { status: 403 })
+  }
+
+  let body: { key?: string; value?: string }
+  try {
+    body = (await request.json()) as { key?: string; value?: string }
+  } catch {
+    return NextResponse.json({ error: 'Invalid JSON' }, { status: 400 })
+  }
+
+  const key = String(body.key ?? '').trim() as LinkKey
+  const value = String(body.value ?? '').trim()
+
+  if (!key || !(key in LINKS)) {
+    return NextResponse.json({ error: 'Unknown link key' }, { status: 400 })
+  }
+  if (!value) {
+    return NextResponse.json({ error: 'Value cannot be empty' }, { status: 400 })
+  }
+
+  await setLink(key, value)
+  return NextResponse.json({ ok: true })
+}