feat(songs): 歌曲管理支持批量驳回、投稿留言自动审查与排期范围可见性过滤

- 新增 /api/admin/songs/batch-reject.post 批量驳回接口（事务清排期/投票/扣接纳数/黑名单去重/异步通知）
- requireSongAdmin 三角色校验 + createApiError 统一错误包装
- scheduleDaysBefore/After 四字段排期可见范围限制（开放 API 与公开排期接口三处缓存路径 + DB 条件过滤）
- submissionNoteAutoModeration 基于黑名单 KEYWORD/LANGUAGE/GENRE 自动判定留言 publicStatus，命中自动关闭 submissionNotePublic
- 更新 songs/request.post 与 songs/[id]/update.put 接入自动审查逻辑

server/utils/schedule-visibility.ts

@@ -0,0 +1,52 @@
+export interface ScheduleVisibilityRange {
+  startAt: Date | null
+  endAt: Date | null
+}
+
+export interface VisibilitySettingsLike {
+  scheduleDaysBeforeEnabled?: boolean | null
+  scheduleDaysBefore?: number | null
+  scheduleDaysAfterEnabled?: boolean | null
+  scheduleDaysAfter?: number | null
+}
+
+export function resolveScheduleVisibilityRange(
+  settings: VisibilitySettingsLike | null | undefined,
+  referenceDate = new Date()
+): ScheduleVisibilityRange {
+  const today = new Date(
+    referenceDate.getFullYear(),
+    referenceDate.getMonth(),
+    referenceDate.getDate()
+  )
+
+  let startAt: Date | null = null
+  let endAt: Date | null = null
+
+  if (settings?.scheduleDaysBeforeEnabled) {
+    const days = Math.max(0, Number(settings.scheduleDaysBefore) || 0)
+    const d = new Date(today)
+    d.setDate(d.getDate() - days)
+    startAt = d
+  }
+
+  if (settings?.scheduleDaysAfterEnabled) {
+    const days = Math.max(0, Number(settings.scheduleDaysAfter) || 0)
+    const d = new Date(today)
+    d.setDate(d.getDate() + days + 1)
+    endAt = d
+  }
+
+  return { startAt, endAt }
+}
+
+export function isPlayDateInRange(
+  playDate: Date | string | null | undefined,
+  range: ScheduleVisibilityRange
+): boolean {
+  if (!playDate) return true
+  const d = new Date(playDate)
+  if (range.startAt && d.getTime() < range.startAt.getTime()) return false
+  if (range.endAt && d.getTime() >= range.endAt.getTime()) return false
+  return true
+}