fix(music): setTimeout 정리 + useCallback 폴링 deps

- TrendsTab: useRef로 타이머 ID 추적 후 언마운트 시 clearTimeout 호출 (stale setState 방지)
- VideoProjectsTab: loadProjects를 useCallback으로 감싸고 폴링 useEffect deps에 추가

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/pages/music/components/TrendsTab.jsx

@@ -1,5 +1,5 @@
 // src/pages/music/components/TrendsTab.jsx
-import { useState, useEffect } from 'react';
+import { useState, useEffect, useRef } from 'react';
 import {
     getLatestTrendReport, getTrendReports,
     getMarketSuggestions, triggerYoutubeResearch,
@@ -28,6 +28,9 @@ export default function TrendsTab() {
     const [loading,        setLoading]        = useState(true);
     const [researchMsg,    setResearchMsg]    = useState('');
 
+    const researchTimerRef = useRef(null);
+    const copyTimerRef     = useRef(null);
+
     const loadAll = async () => {
         setLoading(true);
         try {
@@ -48,12 +51,20 @@ export default function TrendsTab() {
 
     useEffect(() => { loadAll(); }, []);
 
+    useEffect(() => {
+        return () => {
+            clearTimeout(researchTimerRef.current);
+            clearTimeout(copyTimerRef.current);
+        };
+    }, []);
+
     const handleResearch = async () => {
         setResearching(true);
         try {
             await triggerYoutubeResearch();
             setResearchMsg('수집이 시작되었습니다. 잠시 후 새로고침하세요.');
-            setTimeout(() => setResearchMsg(''), 4000);
+            clearTimeout(researchTimerRef.current);
+            researchTimerRef.current = setTimeout(() => setResearchMsg(''), 4000);
         } catch (e) {
             console.error('triggerYoutubeResearch:', e);
         } finally {
@@ -64,7 +75,8 @@ export default function TrendsTab() {
     const handleCopy = (text, idx) => {
         navigator.clipboard.writeText(text).then(() => {
             setCopiedIdx(idx);
-            setTimeout(() => setCopiedIdx(null), 2000);
+            clearTimeout(copyTimerRef.current);
+            copyTimerRef.current = setTimeout(() => setCopiedIdx(null), 2000);
         });
     };
 

src/pages/music/components/VideoProjectsTab.jsx

@@ -1,5 +1,5 @@
 // src/pages/music/components/VideoProjectsTab.jsx
-import { useState, useEffect, useRef } from 'react';
+import { useState, useEffect, useRef, useCallback } from 'react';
 import {
     createVideoProject, getVideoProjects,
     renderVideoProject, exportVideoProject, deleteVideoProject,
@@ -26,14 +26,14 @@ export default function VideoProjectsTab({ library, initialTrackId, onClearIniti
         }
     }, [initialTrackId]);
 
-    const loadProjects = async () => {
+    const loadProjects = useCallback(async () => {
         try {
             const data = await getVideoProjects();
             setProjects(Array.isArray(data) ? data : data.projects ?? []);
         } catch (e) {
             console.error('getVideoProjects:', e);
         }
-    };
+    }, []);
 
     useEffect(() => { loadProjects(); }, []);
 
@@ -49,7 +49,7 @@ export default function VideoProjectsTab({ library, initialTrackId, onClearIniti
         return () => {
             if (pollRef.current) { clearInterval(pollRef.current); pollRef.current = null; }
         };
-    }, [projects]);
+    }, [projects, loadProjects]);
 
     const toggleCountry = (c) => {
         setCountries(prev =>