feat(web-ui): Create 탭 배치 생성 섹션 + BatchProgress 폴링

src/api.js

@@ -674,3 +674,8 @@ export const getYoutubeAuthUrl   = ()               => apiGet('/api/music/youtub
 export const getYoutubeStatus    = ()               => apiGet('/api/music/youtube/status');
 export const disconnectYoutube   = ()               => apiPost('/api/music/youtube/disconnect');
 
+// === Batch generation ===
+export const startBatchGen   = (payload)        => apiPost('/api/music/generate-batch', payload);
+export const getBatchJob     = (id)             => apiGet(`/api/music/generate-batch/${id}`);
+export const listBatchJobs   = (status='all')   => apiGet(`/api/music/generate-batch?status=${status}`);
+