The announcements page is a public, crawlable route but its page.tsx is
'use client', so it can't export metadata itself and falls back to the
root app/layout.tsx. Add a server-component layout.tsx under
app/(home)/announcements/ that exports route-specific metadata (title,
description, canonical, OpenGraph, Twitter) in the same shape as the
neighboring /blog, /changelog, /contact, /privacy, /terms routes.
page.tsx is unchanged.
Canonical URL matches app/layout.tsx's metadataBase
(https://surfsense.com).
Fixes#1244
