Portal: footer links prefetch into www.lanetti.fi and log CORS errors on every page

Imported from GitHub issue El-SaMa/oma#225 by @El-SaMa.

---

Every signed-in portal page logs console errors like:

Access to fetch at 'https://www.lanetti.fi/status' (redirected from 'https://oma.lanetti.fi/status?_rsc=…') … blocked by CORS policy

Same for /legal, /legal/privacy, /legal/terms, /tutorials, /news and news articles. Next.js Link prefetches these, oma.lanetti.fi redirects them to www.lanetti.fi, and the RSC fetch fails cross-origin (net::ERR_FAILED). Seen on /apps/uptime, /dashboard and the other app pages (2026-10-15 headless run).

Fix: link straight to https://www.lanetti.fi/... with a plain <a> (or prefetch={false}) in the portal chrome/footer.