feat(ui): add AnimatedTextCycle component and framer-motion

- add src/components/ui/animated-text-cycle.tsx (animated word cycle using framer-motion)
- add framer-motion dependency to package.json and update bun.lock (includes motion-dom / motion-utils)
- update About link to use YouTube playlist URL
- remove unused background images (public/bg.avif, public/bg.png) and update public/char.avif

src/app/page.tsx

@@ -15,7 +15,7 @@ export default function Home() {
           <p>최근에는 정보보안 분야 중 웹 해킹에 관심이 많습니다.</p>
           <br />
           <p>대표적인 프로젝트들은 아래와 같습니다.</p>
-          <a href="https://www.youtube.com/watch?v=XTdqpdTMZbw&list=PLZeYZotn5_IOJDek6e35NKzUtJm09yxZD">Effect Playing Contest 2025 Broadcast Develop</a><br />
+          <a href="https://www.youtube.com/playlist?list=PLZeYZotn5_IOJDek6e35NKzUtJm09yxZD">Effect Playing Contest 2025 Broadcast Develop</a><br />
           <a href="https://github.com/imnyang/today.isangjeong">today.isangjeong</a>
         </div>