fix: React saveBatch 요청 body 객체 래핑 제거

saveBatch API 호출 시 { entries } 객체로 감싸서 보내던 것을
배열 직접 전송으로 수정. 백엔드 @RequestBody List<>와 불일치로
임시저장/제출 시 status가 null로 표시되던 버그 해결.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

wtm-frontend-react/src/modules/timesheet/timesheet.service.ts

@@ -5,7 +5,7 @@ const BASE = '/api/wtm/timesheets';
 export const timesheetService = {
   getWeekly: (weekStart: string) => api.get(`${BASE}/week`, { params: { weekStart } }),
   saveEntry: (tsId: number, entry: unknown) => api.post(`${BASE}/${tsId}/entries`, entry),
-  saveBatch: (tsId: number, entries: unknown[]) => api.put(`${BASE}/${tsId}/entries/batch`, { entries }),
+  saveBatch: (tsId: number, entries: unknown[]) => api.put(`${BASE}/${tsId}/entries/batch`, entries),
   deleteEntry: (tsId: number, entryId: number) => api.delete(`${BASE}/${tsId}/entries/${entryId}`),
   submit: (tsId: number) => api.post(`${BASE}/${tsId}/submit`),
   getHistory: (params: Record<string, unknown>) => api.get(`${BASE}/history`, { params }),