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/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 =>