style: apply Primary Color (#4E77FF) to AppHeader active tabs and Hero Orchestration highlights

refer_landing_page/app/page.tsx

@@ -63,7 +63,7 @@ export default function HomePage() {
       {/* Hero Section */}
       <section className="relative">
         <div className="mb-4">
-          <span className="font-mono text-xs tracking-widest uppercase text-vermillion font-bold">
+          <span className="font-mono text-xs tracking-widest uppercase text-cobalt-dark dark:text-cobalt font-bold">
             Kyungpook National University · AI Agent Networking Lab (ANL)
           </span>
         </div>
@@ -72,7 +72,7 @@ export default function HomePage() {
           <div className="lg:col-span-7 space-y-6 lg:pt-4">
             <h1 className="font-serif text-4xl sm:text-5xl lg:text-6xl font-normal text-ink leading-tight">
               Multi-Agent <br />
-              <span className="italic font-serif text-vermillion">Orchestration</span>
+              <span className="italic font-serif text-cobalt-dark dark:text-cobalt">Orchestration</span>
             </h1>
             <p className="text-ink-mute text-base sm:text-lg leading-relaxed max-w-2xl">
               AI 에이전트 네트워크 연구실(ANL)은 멀티 AI 에이전트 오케스트레이션을 위해 서로 소통하고 협력하는 에이전트 네트워킹 기술과 표준 프레임워크 기술을 연구합니다.