feat(web-admin): sync lump-sum deadline to last due date

Add applyLumpSumDeadlineToLastDueDate for dj payment schedules,
skipping locked or void rows.

Co-authored-by: Cursor <cursoragent@cursor.com>

web-admin/src/utils/protocol-sample-payment.ts

@@ -440,3 +440,22 @@ export function shouldAutoFillLastPeriodDue(opts: {
 }): boolean {
   return !opts.lastManualOverride && !opts.lastLocked
 }
+
+/** 趸交：将截止时间写入未作废批次中的最后一期 dueDate；锁定则跳过 */
+export function applyLumpSumDeadlineToLastDueDate<T extends ScheduleLike>(
+  schedules: T[],
+  deadline: string | null | undefined,
+  isLocked: (sch: T) => boolean
+): T[] {
+  const due = String(deadline || '').trim()
+  const activeIdx: number[] = []
+  schedules.forEach((s, i) => {
+    if (String(s.scheduleStatus || 'open') !== 'void') activeIdx.push(i)
+  })
+  if (!activeIdx.length) return schedules.map((s) => ({ ...s }))
+  const lastIdx = activeIdx[activeIdx.length - 1]
+  if (isLocked(schedules[lastIdx])) {
+    return schedules.map((s) => ({ ...s }))
+  }
+  return schedules.map((s, i) => (i === lastIdx ? { ...s, dueDate: due } : { ...s }))
+}