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-form.tsx

@@ -23,6 +23,8 @@ import type { Announcement } from "../types"
 
 type Mode = "create" | "edit"
 
+type FieldErrors = Record<string, string[]>
+
 export function AnnouncementForm({
   mode,
   announcement,
@@ -37,14 +39,21 @@ export function AnnouncementForm({
   const t = useTranslations("announcements")
   const router = useRouter()
   const [isWorking, setIsWorking] = useState(false)
+  const [fieldErrors, setFieldErrors] = useState<FieldErrors>({})
 
   const [type, setType] = useState<string>(announcement?.type ?? "school")
   const [status, setStatus] = useState<string>(announcement?.status ?? "draft")
   const [targetGradeId, setTargetGradeId] = useState<string>(announcement?.targetGradeId ?? "")
   const [targetClassId, setTargetClassId] = useState<string>(announcement?.targetClassId ?? "")
 
+  const getFieldError = (field: string): string | null => {
+    const errs = fieldErrors[field]
+    return errs && errs.length > 0 ? errs[0] : null
+  }
+
   const handleSubmit = async (formData: FormData) => {
     setIsWorking(true)
+    setFieldErrors({})
     try {
       formData.set("type", type)
       formData.set("status", status)
@@ -72,6 +81,10 @@ export function AnnouncementForm({
         router.push("/admin/announcements")
         router.refresh()
       } else {
+        // 展示字段级错误（来自 Zod superRefine 校验）
+        if (res.errors) {
+          setFieldErrors(res.errors)
+        }
         toast.error(res.message || t("messages.updateFailed"))
       }
     } catch {
@@ -98,7 +111,11 @@ export function AnnouncementForm({
               placeholder={t("form.titlePlaceholder")}
               defaultValue={announcement?.title ?? ""}
               required
+              aria-invalid={!!getFieldError("title")}
             />
+            {getFieldError("title") ? (
+              <p className="text-destructive text-xs">{getFieldError("title")}</p>
+            ) : null}
           </div>
 
           <div className="grid gap-2">
@@ -110,7 +127,11 @@ export function AnnouncementForm({
               className="min-h-[160px]"
               defaultValue={announcement?.content ?? ""}
               required
+              aria-invalid={!!getFieldError("content")}
             />
+            {getFieldError("content") ? (
+              <p className="text-destructive text-xs">{getFieldError("content")}</p>
+            ) : null}
           </div>
 
           <div className="grid grid-cols-1 gap-4 md:grid-cols-2">
@@ -148,7 +169,7 @@ export function AnnouncementForm({
               <div className="grid gap-2 md:col-span-2">
                 <Label>{t("form.targetGrade")}</Label>
                 <Select value={targetGradeId} onValueChange={setTargetGradeId}>
-                  <SelectTrigger>
+                  <SelectTrigger aria-invalid={!!getFieldError("targetGradeId")}>
                     <SelectValue placeholder={t("form.targetGradePlaceholder")} />
                   </SelectTrigger>
                   <SelectContent>
@@ -160,6 +181,9 @@ export function AnnouncementForm({
                   </SelectContent>
                 </Select>
                 <input type="hidden" name="targetGradeId" value={targetGradeId} />
+                {getFieldError("targetGradeId") ? (
+                  <p className="text-destructive text-xs">{getFieldError("targetGradeId")}</p>
+                ) : null}
               </div>
             ) : null}
 
@@ -167,7 +191,7 @@ export function AnnouncementForm({
               <div className="grid gap-2 md:col-span-2">
                 <Label>{t("form.targetClass")}</Label>
                 <Select value={targetClassId} onValueChange={setTargetClassId}>
-                  <SelectTrigger>
+                  <SelectTrigger aria-invalid={!!getFieldError("targetClassId")}>
                     <SelectValue placeholder={t("form.targetClassPlaceholder")} />
                   </SelectTrigger>
                   <SelectContent>
@@ -179,6 +203,9 @@ export function AnnouncementForm({
                   </SelectContent>
                 </Select>
                 <input type="hidden" name="targetClassId" value={targetClassId} />
+                {getFieldError("targetClassId") ? (
+                  <p className="text-destructive text-xs">{getFieldError("targetClassId")}</p>
+                ) : null}
               </div>
             ) : null}
           </div>

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}