style: apply accessibility badge contrast refinements and update primary color to #4E77FF

refer_landing_page/app/_components/DirectionsBlock.tsx

@@ -48,7 +48,7 @@ export function DirectionsBlock() {
               <span className="font-mono text-xs uppercase tracking-wider text-ink-mute w-20 pt-0.5">
                 관련 기관
               </span>
-              <div className="flex flex-wrap gap-x-4 gap-y-1 text-xs font-mono text-cobalt">
+              <div className="flex flex-wrap gap-x-4 gap-y-1 text-xs font-mono text-cobalt-dark dark:text-cobalt">
                 <a href="http://www.knu.ac.kr/" target="_blank" rel="noreferrer" className="hover:underline">
                   경북대학교 (KNU) ↗
                 </a>