fix(ux): apply UX quick wins (#54)

Get started links to registration and says an admin approves accounts.
Back navigation restores the library scroll; search no longer fills history.
Steam and PSN unlink ask first. Any close marks news as seen.
Confetti plays only when the level rises on the page.
Count-ups respect reduced motion. Html lang follows the UI language.
Add a 404 page, translated role and dialog close label.

src/pages/LandingPage.jsx

@@ -131,9 +131,10 @@ export default function LandingPage() {
                             {active ? (
                                 <Link to="/dashboard">{t('NAV.TO_DASHBOARD')}<ArrowRight/></Link>
                             ) : (
-                                <Link to="/login">{t('MAIN.GET_STARTED')}<ArrowRight/></Link>
+                                <Link to="/register">{t('MAIN.GET_STARTED')}<ArrowRight/></Link>
                             )}
                         </Button>
+                        {!active && <p className="mt-4 text-sm text-muted-foreground">{t('MAIN.APPROVAL_HINT')}</p>}
                     </div>
                 </section>