feat(announcements,messaging): 公告与消息模块审计重构 — i18n + Error Boundary + a11y

- 新增审计报告 docs/architecture/audit/announcements-messages-audit-report.md
- 新增中英双语 i18n 字典 announcements.json / messages.json（11/13 个命名空间）
- 重构所有 announcements 和 messaging 组件接入 next-intl（useTranslations）
- 所有页面 page.tsx 使用 generateMetadata + getTranslations 替代硬编码 metadata
- 新增 7 个 error.tsx 错误边界（4 公告 + 3 消息），统一 EmptyState + i18n + 重试
- a11y 改进：announcement-card / message-list / notification-dropdown 添加 aria-label
- 同步架构图 004 和 005：i18n.messages 清单 + 已知问题修复记录

src/modules/messaging/components/message-list.tsx

@@ -3,6 +3,7 @@
 import { useEffect, useMemo, useState } from "react"
 import Link from "next/link"
 import { Mail, MailOpen, Plus, Send, Inbox, Search, Loader2 } from "lucide-react"
+import { useTranslations } from "next-intl"
 
 import { Badge } from "@/shared/components/ui/badge"
 import { Button } from "@/shared/components/ui/button"
@@ -28,6 +29,7 @@ export function MessageList({
   currentUserId: string
   initialType?: MessageType
 }) {
+  const t = useTranslations("messages")
   const [tab, setTab] = useState<Tab>(initialType === "sent" ? "sent" : "inbox")
   const [keyword, setKeyword] = useState("")
   const [searchResults, setSearchResults] = useState<{ kw: string; tab: Tab; items: Message[] } | null>(null)
@@ -80,11 +82,11 @@ export function MessageList({
           <TabsList>
             <TabsTrigger value="inbox" className="gap-2">
               <Inbox className="h-4 w-4" />
-              Inbox
+              {t("tabs.inbox")}
             </TabsTrigger>
             <TabsTrigger value="sent" className="gap-2">
               <Send className="h-4 w-4" />
-              Sent
+              {t("tabs.sent")}
             </TabsTrigger>
           </TabsList>
         </Tabs>
@@ -92,7 +94,7 @@ export function MessageList({
           <Button asChild>
             <Link href="/messages/compose">
               <Plus className="mr-2 h-4 w-4" />
-              Compose
+              {t("actions.compose")}
             </Link>
           </Button>
         ) : null}
@@ -100,26 +102,27 @@ export function MessageList({
 
       {/* 搜索框 */}
       <div className="relative">
-        <Search className="text-muted-foreground absolute left-3 top-1/2 size-4 -translate-y-1/2" />
+        <Search className="text-muted-foreground absolute left-3 top-1/2 size-4 -translate-y-1/2" aria-hidden="true" />
         <Input
           type="search"
-          placeholder="Search messages by subject or content..."
+          aria-label={t("search.placeholder")}
+          placeholder={t("search.placeholder")}
           value={keyword}
           onChange={(e) => setKeyword(e.target.value)}
           className="pl-9"
         />
         {searching ? (
-          <Loader2 className="text-muted-foreground absolute right-3 top-1/2 size-4 -translate-y-1/2 animate-spin" />
+          <Loader2 className="text-muted-foreground absolute right-3 top-1/2 size-4 -translate-y-1/2 animate-spin" aria-hidden="true" />
         ) : null}
       </div>
 
       {filtered.length === 0 ? (
         <EmptyState
-          title={tab === "inbox" ? "Inbox is empty" : "No sent messages"}
+          title={tab === "inbox" ? t("empty.inboxEmpty") : t("empty.sentEmpty")}
           description={
             tab === "inbox"
-              ? "You have no incoming messages yet."
-              : "You have not sent any messages yet."
+              ? t("empty.inboxEmptyDesc")
+              : t("empty.sentEmptyDesc")
           }
           icon={Mail}
           className="h-auto border-none shadow-none"
@@ -131,23 +134,23 @@ export function MessageList({
             const counterpart = isReceived ? m.senderName : m.receiverName
             const unread = isReceived && !m.isRead
             return (
-              <Link key={m.id} href={`/messages/${m.id}`} className="block">
+              <Link key={m.id} href={`/messages/${m.id}`} className="block" aria-label={m.subject ?? t("meta.noSubject")}>
                 <Card className={cn("transition-colors hover:bg-accent/50", unread && "border-primary/40")}>
                   <CardHeader className="flex flex-row items-start justify-between gap-2 space-y-0 pb-3">
                     <div className="space-y-1">
                       <div className="flex items-center gap-2">
                         {unread ? (
-                          <Mail className="h-4 w-4 text-primary" />
+                          <Mail className="h-4 w-4 text-primary" aria-hidden="true" />
                         ) : (
-                          <MailOpen className="text-muted-foreground h-4 w-4" />
+                          <MailOpen className="text-muted-foreground h-4 w-4" aria-hidden="true" />
                         )}
                         <span className={cn("text-sm font-medium", unread && "text-primary")}>
-                          {m.subject ?? "(no subject)"}
+                          {m.subject ?? t("meta.noSubject")}
                         </span>
-                        {unread ? <Badge variant="default" className="text-xs">New</Badge> : null}
+                        {unread ? <Badge variant="default" className="text-xs">{t("status.new")}</Badge> : null}
                       </div>
                       <p className="text-muted-foreground text-xs">
-                        {isReceived ? "From" : "To"}: {counterpart ?? "Unknown"}
+                        {isReceived ? t("meta.from") : t("meta.to")}: {counterpart ?? t("meta.unknown")}
                       </p>
                     </div>
                     <span className="text-muted-foreground shrink-0 text-xs">