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/grade-class-options.ts

@@ -0,0 +1,45 @@
+import { and, isNotNull, eq, ne, sql } from 'drizzle-orm'
+import { db } from '~/drizzle/db'
+import { users, gradeClasses } from '~/drizzle/schema'
+import { resolveGradeClassOptions, type GradeClassOption } from './grade-class-core'
+
+export async function fetchGradeClassOptions(): Promise<GradeClassOption[]> {
+  const [configRows, userRows] = await Promise.all([
+    db.select({
+      grade: gradeClasses.grade,
+      class: gradeClasses.class
+    }).from(gradeClasses),
+    db
+      .selectDistinct({
+        grade: users.grade,
+        class: users.class
+      })
+      .from(users)
+      .where(and(eq(users.status, 'active'), isNotNull(users.grade), isNotNull(users.class)))
+  ])
+
+  return resolveGradeClassOptions(configRows, userRows)
+}
+
+export async function isGradeClassValid(grade: string, studentClass: string): Promise<boolean> {
+  const configHit = await db.query.gradeClasses.findFirst({
+    where: (t, { eq: eq_, and: and_ }) => and_(eq_(t.grade, grade), eq_(t.class, studentClass)),
+    columns: { id: true }
+  })
+
+  if (configHit) return true
+
+  const configCount = await db
+    .select({ count: () => sql<number>`count(*)::int` })
+    .from(gradeClasses)
+    .where(and(ne(gradeClasses.grade, ''), ne(gradeClasses.class, '')))
+  if ((configCount[0]?.count || 0) > 0) return false
+
+  const userHit = await db.query.users.findFirst({
+    where: (t, { eq: eq_, and: and_ }) =>
+      and_(eq_(t.status, 'active'), eq_(t.grade, grade), eq_(t.class, studentClass)),
+    columns: { id: true }
+  })
+
+  return Boolean(userHit)
+}