곡 상세 페이지 트랙 변경 시 스크롤/애니메이션 개선

- ScrollToTop: PC 레이아웃의 main 요소 스크롤 초기화 추가
- TrackDetail: key prop으로 트랙 변경 시 컴포넌트 리마운트
- TrackDetail: main 요소 스크롤 초기화 (PC는 main에서 스크롤)
- 수록곡 선택 시 Link 대신 button + navigate 사용

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

frontend/src/components/common/ScrollToTop.jsx

@@ -16,6 +16,12 @@ function ScrollToTop() {
     if (mobileContent) {
       mobileContent.scrollTop = 0;
     }
+
+    // PC 레이아웃 스크롤 컨테이너 초기화
+    const main = document.querySelector('main');
+    if (main) {
+      main.scrollTop = 0;
+    }
   }, [pathname]);
 
   return null;

frontend/src/pages/mobile/album/TrackDetail.jsx

@@ -1,4 +1,4 @@
-import { useState, useMemo, useEffect } from 'react';
+import { useState, useMemo, useEffect, useLayoutEffect } from 'react';
 import { useParams, useNavigate, Link } from 'react-router-dom';
 import { useQuery } from '@tanstack/react-query';
 import { motion } from 'framer-motion';
@@ -40,6 +40,11 @@ function MobileTrackDetail() {
   const youtubeVideoId = useMemo(() => getYoutubeVideoId(track?.video_url), [track?.video_url]);
   const videoLabel = track?.video_type === 'special' ? '스페셜 영상' : '뮤직비디오';
 
+  // 트랙 변경 시 스크롤 맨 위로
+  useLayoutEffect(() => {
+    window.scrollTo({ top: 0, behavior: 'instant' });
+  }, [trackTitle]);
+
   // 가사 펼침 상태
   const [showFullLyrics, setShowFullLyrics] = useState(false);
 
@@ -93,7 +98,7 @@ function MobileTrackDetail() {
   }
 
   return (
-    <div className="pb-4">
+    <div key={trackTitle} className="pb-4">
       {/* 트랙 정보 헤더 */}
       <motion.div
         initial={{ opacity: 0, y: 20 }}

frontend/src/pages/pc/public/album/TrackDetail.jsx

@@ -1,4 +1,4 @@
-import { useMemo } from 'react';
+import { useMemo, useLayoutEffect } from 'react';
 import { useParams, useNavigate, Link } from 'react-router-dom';
 import { useQuery } from '@tanstack/react-query';
 import { motion } from 'framer-motion';
@@ -40,6 +40,14 @@ function PCTrackDetail() {
   const youtubeVideoId = useMemo(() => getYoutubeVideoId(track?.video_url), [track?.video_url]);
   const videoLabel = track?.video_type === 'special' ? '스페셜 영상' : '뮤직비디오';
 
+  // 트랙 변경 시 스크롤 맨 위로
+  useLayoutEffect(() => {
+    const main = document.querySelector('main');
+    if (main) {
+      main.scrollTop = 0;
+    }
+  }, [trackTitle]);
+
   if (loading) {
     return (
       <motion.div
@@ -61,7 +69,13 @@ function PCTrackDetail() {
   }
 
   return (
-    <motion.div initial={{ opacity: 0 }} animate={{ opacity: 1 }} transition={{ duration: 0.3 }} className="py-12">
+    <motion.div
+      key={trackTitle}
+      initial={{ opacity: 0 }}
+      animate={{ opacity: 1 }}
+      transition={{ duration: 0.3 }}
+      className="py-12"
+    >
       <div className="max-w-7xl mx-auto px-6">
         {/* 브레드크럼 네비게이션 */}
         <div className="flex items-center gap-2 text-sm text-gray-500 mb-8">
@@ -218,11 +232,18 @@ function PCTrackDetail() {
                 {track.otherTracks?.map((t) => {
                   const isCurrent = t.title === track.title;
                   return (
-                    <Link
+                    <button
                       key={t.id}
-                      to={`/album/${encodeURIComponent(track.album?.title || albumName)}/track/${encodeURIComponent(t.title)}`}
-                      replace={!isCurrent}
-                      className={`group flex items-center gap-3 px-3 py-2.5 rounded-xl transition-all ${
+                      type="button"
+                      onClick={() => {
+                        if (!isCurrent) {
+                          navigate(
+                            `/album/${encodeURIComponent(track.album?.title || albumName)}/track/${encodeURIComponent(t.title)}`,
+                            { replace: true }
+                          );
+                        }
+                      }}
+                      className={`w-full group flex items-center gap-3 px-3 py-2.5 rounded-xl transition-all ${
                         isCurrent ? 'bg-primary text-white' : 'hover:bg-gray-50'
                       }`}
                     >
@@ -259,7 +280,7 @@ function PCTrackDetail() {
                       <span className={`text-xs tabular-nums ${isCurrent ? 'text-white/70' : 'text-gray-400'}`}>
                         {t.duration || ''}
                       </span>
-                    </Link>
+                    </button>
                   );
                 })}
               </div>