refactor(announcements,messaging,notifications): V1+V2 审计重构 — i18n 命名空间独立 + 通知标题 i18n 化 + 服务端过滤 + 编排下沉 + 表单错误展示 + 架构图同步

V1 改进（已完成）:
- P0-4/P1-4/P1-5: 通知组件和 CRUD Action 从 messaging 迁移至 notifications 模块
- P1-5: 新增 getMessagesPageData / getAdminAnnouncementsPageData 编排函数
- P1-6: announcements schema 添加 superRefine 条件校验
- P1-7: 新增 useMessageSearch hook（防抖 + 请求竞态取消）+ 客户端分页 UI
- P1-9: deleteMessage 事务化
- P2-11: 全模块 trackEvent 埋点
- 全模块 i18n 接入 + Error Boundary + a11y 改进

V2 改进（本次完成）:
- V2-P0-1: 通知 i18n 命名空间独立（notifications.json），useTranslations 从 "messages" 切换到 "notifications"
- V2-P0-2: 公告/消息通知标题 i18n 化，Server Action 中使用 getTranslations 生成通知标题
- V2-P1-1: AnnouncementList 纯服务端过滤，移除客户端 useState/useMemo
- V2-P1-2: MessageList 客户端过滤仅在初始数据时执行，搜索结果由服务端按 tab 过滤
- V2-P1-3: 消息详情页编排下沉，新增 getMessageDetailPageData 编排函数
- V2-P1-4: 表单服务端校验错误展示（fieldErrors + aria-invalid）
- V2-P2-1: 轮询间隔常量化（POLL_INTERVAL_MS）
- V2-P2-2: 架构图同步（004 + 005）

src/modules/notifications/actions.ts

@@ -5,21 +5,31 @@
  *
  * - sendNotificationAction: 发送通知给指定用户（需要 MESSAGE_SEND 权限）
  * - sendClassNotificationAction: 发送班级通知（教师权限，按班级查询学生后批量发送）
+ * - getNotificationsAction / markNotificationAsReadAction / markAllNotificationsAsReadAction / getUnreadNotificationCountAction: 站内通知 CRUD
  *
  * 权限说明:
  * 项目无独立 NOTIFICATION_SEND 权限点，复用 MESSAGE_SEND（教师/管理员/年级主任均拥有）。
  * 班级通知按教师所教班级过滤，确保教师只能给自己班级发通知。
+ * 站内通知读取/标记已读复用 MESSAGE_READ 权限（任何能读消息的用户都能查看通知）。
  */
 
+import { revalidatePath } from "next/cache"
 import { z } from "zod"
 import { PermissionDeniedError, requirePermission } from "@/shared/lib/auth-guard"
+import { trackEvent } from "@/shared/lib/track-event"
 import { Permissions } from "@/shared/types/permissions"
 import type { ActionState } from "@/shared/types/action-state"
 
 import { getClassExists, getStudentIdsByClassId } from "@/modules/classes/data-access"
 
 import { sendNotification, sendBatchNotifications } from "./dispatcher"
-import type { NotificationPayload, ChannelSendResult } from "./types"
+import {
+  getNotifications,
+  markNotificationAsRead,
+  markAllNotificationsAsRead,
+  getUnreadNotificationCount,
+} from "./data-access"
+import type { NotificationPayload, ChannelSendResult, Notification } from "./types"
 
 /**
  * Zod 校验：通知负载（sendNotificationAction 入参）
@@ -157,3 +167,101 @@ export async function sendClassNotificationAction(
     return { success: false, message: "Unexpected error" }
   }
 }
+
+// ---------------------------------------------------------------------------
+// 站内通知 CRUD Server Actions
+//
+// 这些 Action 从 messaging/actions.ts 迁移而来，使 notifications 模块成为
+// 通知相关 UI 组件的唯一数据来源，消除 messaging 与 notifications 在 UI 层
+// 的双向耦合。权限复用 MESSAGE_READ（任何能读消息的用户都能查看通知）。
+// ---------------------------------------------------------------------------
+
+/** Zod 校验：通知 ID 路径参数 */
+const NotificationIdSchema = z.string().trim().min(1)
+
+/**
+ * 获取当前用户的通知列表（分页）。
+ */
+export async function getNotificationsAction(
+  params?: { page?: number; pageSize?: number; unreadOnly?: boolean }
+): Promise<ActionState<{ items: Notification[]; total: number; page: number; pageSize: number; totalPages: number }>> {
+  try {
+    const ctx = await requirePermission(Permissions.MESSAGE_READ)
+    const result = await getNotifications(ctx.userId, params)
+    return { success: true, data: result }
+  } catch (e) {
+    if (e instanceof PermissionDeniedError) return { success: false, message: e.message }
+    if (e instanceof Error) return { success: false, message: e.message }
+    return { success: false, message: "Unexpected error" }
+  }
+}
+
+/**
+ * 获取当前用户的未读通知计数。
+ */
+export async function getUnreadNotificationCountAction(): Promise<ActionState<number>> {
+  try {
+    const ctx = await requirePermission(Permissions.MESSAGE_READ)
+    const count = await getUnreadNotificationCount(ctx.userId)
+    return { success: true, data: count }
+  } catch (e) {
+    if (e instanceof PermissionDeniedError) return { success: false, message: e.message }
+    if (e instanceof Error) return { success: false, message: e.message }
+    return { success: false, message: "Unexpected error" }
+  }
+}
+
+/**
+ * 将单条通知标记为已读。
+ */
+export async function markNotificationAsReadAction(
+  notificationId: string
+): Promise<ActionState<string>> {
+  try {
+    const ctx = await requirePermission(Permissions.MESSAGE_READ)
+
+    const parsed = NotificationIdSchema.safeParse(notificationId)
+    if (!parsed.success) {
+      return { success: false, message: "Invalid notification id" }
+    }
+
+    await markNotificationAsRead(parsed.data, ctx.userId)
+    revalidatePath("/messages")
+
+    void trackEvent({
+      event: "notification.marked_read",
+      userId: ctx.userId,
+      targetId: parsed.data,
+      targetType: "notification",
+    })
+
+    return { success: true, message: "Notification marked as read" }
+  } catch (e) {
+    if (e instanceof PermissionDeniedError) return { success: false, message: e.message }
+    if (e instanceof Error) return { success: false, message: e.message }
+    return { success: false, message: "Unexpected error" }
+  }
+}
+
+/**
+ * 将当前用户的所有未读通知标记为已读。
+ */
+export async function markAllNotificationsAsReadAction(): Promise<ActionState<string>> {
+  try {
+    const ctx = await requirePermission(Permissions.MESSAGE_READ)
+    await markAllNotificationsAsRead(ctx.userId)
+    revalidatePath("/messages")
+
+    void trackEvent({
+      event: "notification.marked_all_read",
+      userId: ctx.userId,
+      targetType: "notification",
+    })
+
+    return { success: true, message: "All notifications marked as read" }
+  } catch (e) {
+    if (e instanceof PermissionDeniedError) return { success: false, message: e.message }
+    if (e instanceof Error) return { success: false, message: e.message }
+    return { success: false, message: "Unexpected error" }
+  }
+}