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/announcements/components/announcement-list.tsx

@@ -1,6 +1,5 @@
 "use client"
 
-import { useMemo, useState } from "react"
 import Link from "next/link"
 import { useRouter } from "next/navigation"
 import { Plus, Megaphone } from "lucide-react"
@@ -21,6 +20,14 @@ import type { Announcement, AnnouncementStatus } from "../types"
 
 type Filter = "all" | AnnouncementStatus
 
+/**
+ * 公告列表组件。
+ *
+ * 过滤模式：纯服务端过滤。
+ * - Select 切换时更新 URL `?status=`，触发 RSC 重新渲染
+ * - 父页面根据 `?status=` 查询并传入 `announcements` prop
+ * - 组件不再做客户端二次过滤，避免双重过滤逻辑冗余
+ */
 export function AnnouncementList({
   announcements,
   canManage,
@@ -36,7 +43,7 @@ export function AnnouncementList({
 }) {
   const t = useTranslations("announcements")
   const router = useRouter()
-  const [filter, setFilter] = useState<Filter>(initialStatus ?? "all")
+  const filter: Filter = initialStatus ?? "all"
 
   const filterOptions: { value: Filter; label: string }[] = [
     { value: "all", label: t("filter.all") },
@@ -45,13 +52,7 @@ export function AnnouncementList({
     { value: "archived", label: t("filter.archived") },
   ]
 
-  const filtered = useMemo(() => {
-    if (filter === "all") return announcements
-    return announcements.filter((a) => a.status === filter)
-  }, [announcements, filter])
-
-  const handleFilterChange = (value: string) => {
-    setFilter(value as Filter)
+  const handleFilterChange = (value: string): void => {
     const params = new URLSearchParams()
     if (value !== "all") params.set("status", value)
     const qs = params.toString()
@@ -83,11 +84,11 @@ export function AnnouncementList({
         ) : null}
       </div>
 
-      {filtered.length === 0 ? (
+      {announcements.length === 0 ? (
         <EmptyState
           title={t("empty.noAnnouncements")}
           description={
-            announcements.length === 0
+            filter === "all"
               ? t("empty.noAnnouncementsDesc")
               : t("empty.noMatch")
           }
@@ -96,7 +97,7 @@ export function AnnouncementList({
         />
       ) : (
         <div className="grid grid-cols-1 gap-4 md:grid-cols-2 lg:grid-cols-3">
-          {filtered.map((a) => (
+          {announcements.map((a) => (
             <AnnouncementCard
               key={a.id}
               announcement={a}