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/modules/classes/actions-admin.ts

@@ -0,0 +1,151 @@
+"use server"
+
+import { revalidatePath } from "next/cache"
+import { requirePermission, PermissionDeniedError } from "@/shared/lib/auth-guard"
+import { Permissions } from "@/shared/types/permissions"
+
+import type { ActionState } from "@/shared/types/action-state"
+import {
+  createAdminClass,
+  deleteAdminClass,
+  setClassSubjectTeachers,
+  updateAdminClass,
+} from "./data-access"
+import {
+  CreateAdminClassSchema,
+  UpdateAdminClassSchema,
+  DeleteAdminClassSchema,
+} from "./schema"
+import { parseSubjectTeachers } from "./actions-shared"
+
+export async function createAdminClassAction(
+  prevState: ActionState<string> | undefined,
+  formData: FormData
+): Promise<ActionState<string>> {
+  try {
+    await requirePermission(Permissions.CLASS_CREATE)
+
+    const parsed = CreateAdminClassSchema.safeParse({
+      name: formData.get("name"),
+      grade: formData.get("grade"),
+      teacherId: formData.get("teacherId"),
+      schoolName: formData.get("schoolName"),
+      schoolId: formData.get("schoolId"),
+      gradeId: formData.get("gradeId"),
+      homeroom: formData.get("homeroom"),
+      room: formData.get("room"),
+    })
+    if (!parsed.success) {
+      return { success: false, message: "Class name, grade and teacher are required" }
+    }
+
+    const { name, grade, teacherId, schoolName, schoolId, gradeId, homeroom, room } = parsed.data
+
+    try {
+      const id = await createAdminClass({
+        schoolName: schoolName ?? null,
+        schoolId: schoolId ?? null,
+        name,
+        grade,
+        gradeId: gradeId ?? null,
+        teacherId,
+        homeroom: homeroom ?? null,
+        room: room ?? null,
+      })
+      revalidatePath("/admin/school/classes")
+      revalidatePath("/teacher/classes/my")
+      revalidatePath("/teacher/classes/students")
+      revalidatePath("/teacher/classes/schedule")
+      return { success: true, message: "Class created successfully", data: id }
+    } catch (error) {
+      return { success: false, message: error instanceof Error ? error.message : "Failed to create class" }
+    }
+  } catch (e) {
+    if (e instanceof PermissionDeniedError) return { success: false, message: e.message }
+    throw e
+  }
+}
+
+export async function updateAdminClassAction(
+  classId: string,
+  prevState: ActionState | undefined,
+  formData: FormData
+): Promise<ActionState> {
+  try {
+    await requirePermission(Permissions.CLASS_UPDATE)
+
+    const parsed = UpdateAdminClassSchema.safeParse({
+      classId,
+      schoolName: formData.get("schoolName"),
+      schoolId: formData.get("schoolId"),
+      name: formData.get("name"),
+      grade: formData.get("grade"),
+      gradeId: formData.get("gradeId"),
+      teacherId: formData.get("teacherId"),
+      homeroom: formData.get("homeroom"),
+      room: formData.get("room"),
+    })
+    if (!parsed.success) {
+      return { success: false, message: "Missing class id" }
+    }
+
+    const { classId: validatedClassId, schoolName, schoolId, name, grade, gradeId, teacherId, homeroom, room } = parsed.data
+    const subjectTeachers = parseSubjectTeachers(formData.get("subjectTeachers") as string | null)
+
+    try {
+      await updateAdminClass(validatedClassId, {
+        schoolName: schoolName ?? undefined,
+        schoolId: schoolId ?? undefined,
+        name: name ?? undefined,
+        grade: grade ?? undefined,
+        gradeId: gradeId ?? undefined,
+        teacherId: teacherId ?? undefined,
+        homeroom: homeroom ?? undefined,
+        room: room ?? undefined,
+      })
+
+      if (subjectTeachers) {
+        await setClassSubjectTeachers({
+          classId: validatedClassId,
+          assignments: subjectTeachers,
+        })
+      }
+
+      revalidatePath("/admin/school/classes")
+      revalidatePath("/teacher/classes/my")
+      revalidatePath("/teacher/classes/students")
+      revalidatePath("/teacher/classes/schedule")
+      return { success: true, message: "Class updated successfully" }
+    } catch (error) {
+      return { success: false, message: error instanceof Error ? error.message : "Failed to update class" }
+    }
+  } catch (e) {
+    if (e instanceof PermissionDeniedError) return { success: false, message: e.message }
+    throw e
+  }
+}
+
+export async function deleteAdminClassAction(classId: string): Promise<ActionState> {
+  try {
+    await requirePermission(Permissions.CLASS_DELETE)
+
+    const parsed = DeleteAdminClassSchema.safeParse({ classId })
+    if (!parsed.success) {
+      return { success: false, message: "Missing class id" }
+    }
+
+    try {
+      await deleteAdminClass(parsed.data.classId)
+      revalidatePath("/admin/school/classes")
+      revalidatePath("/teacher/classes/my")
+      revalidatePath("/teacher/classes/students")
+      revalidatePath("/teacher/classes/schedule")
+      return { success: true, message: "Class deleted successfully" }
+    } catch (error) {
+      return { success: false, message: error instanceof Error ? error.message : "Failed to delete class" }
+    }
+  } catch (e) {
+    if (e instanceof PermissionDeniedError) return { success: false, message: e.message }
+    throw e
+  }
+}