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/app/(dashboard)/messages/page.tsx

@@ -2,10 +2,9 @@ import { getTranslations } from "next-intl/server"
 
 import { requirePermission } from "@/shared/lib/auth-guard"
 import { Permissions } from "@/shared/types/permissions"
-import { getMessages } from "@/modules/messaging/data-access"
-import { getNotifications } from "@/modules/notifications/data-access"
+import { getMessagesPageData } from "@/modules/messaging/data-access"
 import { MessageList } from "@/modules/messaging/components/message-list"
-import { NotificationList } from "@/modules/messaging/components/notification-list"
+import { NotificationList } from "@/modules/notifications/components/notification-list"
 
 export const dynamic = "force-dynamic"
 
@@ -18,10 +17,8 @@ export default async function MessagesPage() {
   const t = await getTranslations("messages")
   const ctx = await requirePermission(Permissions.MESSAGE_READ)
 
-  const [messagesResult, notificationsResult] = await Promise.all([
-    getMessages({ userId: ctx.userId, type: "all", page: 1, pageSize: 50 }),
-    getNotifications(ctx.userId, { page: 1, pageSize: 20 }),
-  ])
+  const { messages: messagesResult, notifications: notificationsResult } =
+    await getMessagesPageData(ctx.userId)
 
   return (
     <div className="flex h-full flex-col space-y-8 p-8">