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-compose.tsx

@@ -4,6 +4,7 @@ import { useState } from "react"
 import Link from "next/link"
 import { useRouter } from "next/navigation"
 import { toast } from "sonner"
+import { useTranslations } from "next-intl"
 import { ArrowLeft, Send } from "lucide-react"
 
 import { Button } from "@/shared/components/ui/button"
@@ -35,13 +36,14 @@ export function MessageCompose({
   defaultSubject?: string
   backHref?: string
 }) {
+  const t = useTranslations("messages")
   const router = useRouter()
   const [isWorking, setIsWorking] = useState(false)
   const [receiverId, setReceiverId] = useState(defaultReceiverId ?? "")
 
   const handleSubmit = async (formData: FormData) => {
     if (!receiverId) {
-      toast.error("Please select a recipient")
+      toast.error(t("messages.selectRecipient"))
       return
     }
     formData.set("receiverId", receiverId)
@@ -57,10 +59,10 @@ export function MessageCompose({
         router.push("/messages")
         router.refresh()
       } else {
-        toast.error(res.message || "Failed to send message")
+        toast.error(res.message || t("messages.sendFailed"))
       }
     } catch {
-      toast.error("Failed to send message")
+      toast.error(t("messages.sendFailed"))
     } finally {
       setIsWorking(false)
     }
@@ -70,21 +72,21 @@ export function MessageCompose({
     <Card>
       <CardHeader>
         <div className="flex items-center gap-2">
-          <Button asChild variant="ghost" size="icon">
+          <Button asChild variant="ghost" size="icon" aria-label={t("actions.back")}>
             <Link href={backHref}>
               <ArrowLeft className="h-4 w-4" />
             </Link>
           </Button>
-          <CardTitle>{parentMessageId ? "Reply" : "New Message"}</CardTitle>
+          <CardTitle>{parentMessageId ? t("title.reply") : t("title.newMessage")}</CardTitle>
         </div>
       </CardHeader>
       <CardContent>
         <form action={handleSubmit} className="space-y-6">
           <div className="grid gap-2">
-            <Label htmlFor="receiverId">To</Label>
+            <Label htmlFor="receiverId">{t("form.to")}</Label>
             <Select value={receiverId} onValueChange={setReceiverId} disabled={!!defaultReceiverId}>
               <SelectTrigger>
-                <SelectValue placeholder="Select a recipient" />
+                <SelectValue placeholder={t("form.toPlaceholder")} />
               </SelectTrigger>
               <SelectContent>
                 {recipients.map((r) => (
@@ -99,22 +101,22 @@ export function MessageCompose({
           </div>
 
           <div className="grid gap-2">
-            <Label htmlFor="subject">Subject</Label>
+            <Label htmlFor="subject">{t("form.subject")}</Label>
             <Input
               id="subject"
               name="subject"
-              placeholder="Message subject"
+              placeholder={t("form.subjectPlaceholder")}
               defaultValue={defaultSubject ?? ""}
               maxLength={255}
             />
           </div>
 
           <div className="grid gap-2">
-            <Label htmlFor="content">Content</Label>
+            <Label htmlFor="content">{t("form.content")}</Label>
             <Textarea
               id="content"
               name="content"
-              placeholder="Write your message..."
+              placeholder={t("form.contentPlaceholder")}
               className="min-h-[200px]"
               required
             />
@@ -127,15 +129,15 @@ export function MessageCompose({
               onClick={() => router.push(backHref)}
               disabled={isWorking}
             >
-              Cancel
+              {t("actions.cancel")}
             </Button>
             <Button type="submit" disabled={isWorking || !receiverId}>
               {isWorking ? (
-                "Sending..."
+                t("actions.sending")
               ) : (
                 <>
                   <Send className="mr-2 h-4 w-4" />
-                  Send
+                  {t("actions.send")}
                 </>
               )}
             </Button>