feat(app): add error/loading boundaries across all dashboard routes and new routes

- Add error.tsx and loading.tsx boundaries for admin, parent, student, teacher routes

- Add admin announcements edit, audit-logs overview, curriculum-map, invitation-codes, permissions, questions, roles routes

- Add admin elective detail and components, files, course-plans, users, scheduling boundaries

- Add messages group-compose route

- Add parent course-plans, elective, grades report-card, practice routes

- Add student course-plans, elective detail, error-book dialogs, grades report-card, learning study-path, leave, schedule boundaries

- Add teacher attendance report, classes boundaries, course-plans boundaries, elective, exams analytics/edit-rich/all/create/new, grades report-card, homework boundaries, leave, lesson-plans calendar

- Add auth loading, onboarding loading, api cron

src/app/(dashboard)/messages/[id]/page.tsx

@@ -1,11 +1,14 @@
 import { notFound } from "next/navigation"
 import type { Metadata } from "next"
 import type { JSX } from "react"
+import { Suspense } from "react"
 import { getTranslations } from "next-intl/server"
 import { requirePermission } from "@/shared/lib/auth-guard"
 import { Permissions } from "@/shared/types/permissions"
+import { SectionErrorBoundary } from "@/shared/components/section-error-boundary"
 import { getMessageDetailPageData } from "@/modules/messaging/data-access"
 import { MessageDetail } from "@/modules/messaging/components/message-detail"
+import { Skeleton } from "@/shared/components/ui/skeleton"
 
 export const dynamic = "force-dynamic"
 
@@ -14,6 +17,24 @@ export async function generateMetadata(): Promise<Metadata> {
   return { title: t("title.detail") }
 }
 
+/**
+ * P2-9: 消息详情骨架屏。
+ */
+function MessageDetailSkeleton(): JSX.Element {
+  return (
+    <div className="space-y-6" role="status" aria-label="Loading message">
+      <Skeleton className="h-8 w-3/4" />
+      <Skeleton className="h-4 w-1/2" />
+      <Skeleton className="h-32 w-full" />
+      <div className="space-y-2">
+        <Skeleton className="h-4 w-full" />
+        <Skeleton className="h-4 w-5/6" />
+        <Skeleton className="h-4 w-4/5" />
+      </div>
+    </div>
+  )
+}
+
 export default async function MessageDetailPage({
   params,
 }: {
@@ -27,7 +48,12 @@ export default async function MessageDetailPage({
 
   return (
     <div className="flex h-full flex-col p-8">
-      <MessageDetail message={message} currentUserId={ctx.userId} />
+      {/* P2-8 + P2-9: 详情区块 ErrorBoundary 包裹 */}
+      <SectionErrorBoundary namespace="messages">
+        <Suspense fallback={<MessageDetailSkeleton />}>
+          <MessageDetail message={message} currentUserId={ctx.userId} />
+        </Suspense>
+      </SectionErrorBoundary>
     </div>
   )
 }