refactor(school,classes): 完成 school/grade/class 审计全量改进项

P0-1/P0-2: 删除 grade-management 死模块，年级 CRUD 统一由 school 模块负责

P0-3: classes/actions.ts 从 974 行拆分为 6 个职责文件 + barrel re-export

P0-5: 13 个页面 i18n 全量接入（grades/departments/academic-year/classes/insights）

P1-1: 角色硬编码改为 hasAdminScope/hasTeacherScope/hasStudentScope 基于 dataScope.type

P1-3: 新增 SchoolErrorBoundary + SchoolListSkeleton/SchoolCardSkeleton，4 个页面包裹 Error Boundary

P1-4: classes/types.ts 跨领域类型添加归属决策注释

P1-5: schools-view.tsx 拆分为组合模式（SchoolFormDialog + SchoolDeleteDialog + SchoolListToolbar）

P1-6: 新增 getSchoolsForUser/getGradesForUser 权限感知查询函数

P2-1: 抽取 useSchoolData hook，对话框状态管理与 UI 分离

同步更新架构图文档 004/005

src/app/(dashboard)/management/grade/classes/page.tsx

@@ -1,3 +1,7 @@
+import type { Metadata } from "next"
+import type { JSX } from "react"
+
+import { getTranslations } from "next-intl/server"
 import { requirePermission } from "@/shared/lib/auth-guard"
 import { Permissions } from "@/shared/types/permissions"
 import { getGradeManagedClasses, getManagedGrades, getTeacherOptions } from "@/modules/classes/data-access"
@@ -5,8 +9,17 @@ import { GradeClassesClient } from "@/modules/classes/components/grade-classes-v
 
 export const dynamic = "force-dynamic"
 
-export default async function GradeClassesPage() {
+export async function generateMetadata(): Promise<Metadata> {
+  const t = await getTranslations("school")
+  return {
+    title: `${t("classManagement.grade.title")} - Next_Edu`,
+    description: t("classManagement.grade.description"),
+  }
+}
+
+export default async function GradeClassesPage(): Promise<JSX.Element> {
   const ctx = await requirePermission(Permissions.GRADE_MANAGE)
+  const t = await getTranslations("school")
   const userId = ctx.userId
 
   const [classes, teachers, managedGrades] = await Promise.all([
@@ -19,14 +32,12 @@ export default async function GradeClassesPage() {
     <div className="flex h-full flex-col space-y-8 p-8">
       <div className="flex flex-col justify-between space-y-4 md:flex-row md:items-center md:space-y-0">
         <div>
-          <h2 className="text-2xl font-bold tracking-tight">Class Management</h2>
-          <p className="text-muted-foreground">
-            Manage classes for your grades.
-          </p>
+          <h2 className="text-2xl font-bold tracking-tight">{t("classManagement.grade.title")}</h2>
+          <p className="text-muted-foreground">{t("classManagement.grade.description")}</p>
         </div>
       </div>
 
       <GradeClassesClient classes={classes} teachers={teachers} managedGrades={managedGrades} />
     </div>
   )
-}
+}