Add skip option to assessment questions; make profile CEFR display au…

[Lavisha23]

…thoritative

• Every assessment question (grammar, vocab, reading/listening comprehension, both speaking prompts) can now be skipped — Continue is no longer blocked on answering everything, and skipped items are visibly marked. Unanswered items already scored safely as incorrect/ zero server-side, so no scoring changes were needed.
• Settings and the dashboard badge previously trusted whatever was cached in sessionStorage at login/last write, which could show a stale level if that cache fell out of sync. Both now re-fetch the user record from the server (GET /api/auth/me) on mount and refresh the cache, so the profile is authoritative rather than best-effort.
• Settings now shows the full assessment result (all 8 scores + assessment date), not just the level.