Add nav avatar, product icon, spec page and about page updates

- Show profile avatar and formatted name in top nav
- Add product icon to left of brand name in top nav
- Add blue border to ProfileAvatar, add xs size
- Add protected /specificatie page with 5 chapter summaries
- Replace planning button with CV link on about page
- Add Specificatie button on about page
- Show app version + git SHA on about page

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

next-env.d.ts

@@ -1,6 +1,6 @@
 /// <reference types="next" />
 /// <reference types="next/image-types/global" />
-import "./.next/dev/types/routes.d.ts";
+import "./.next/types/routes.d.ts";
 
 // NOTE: This file should not be edited
 // see https://nextjs.org/docs/app/api-reference/config/typescript for more information.