fix: patch P0 security vulnerabilities and critical UX issues across 6 modules

Security: Add admin/layout.tsx auth guard; Add requirePermission() to 12 admin pages

Dashboard: Fix StudentStatsGrid rendering; Fix teacher greeting; Add loading/error boundaries; Fix col-span; Add metadata

Announcements: Fix audience filtering; Add user detail page; Trigger notifications on publish; Pass classes data; Add loading.tsx

Messages: Implement soft delete; Add unread badge with polling; Add notification dropdown polling; Add keyword search; Add quiet hours DND

Management: Add loading/error for 9 admin routes; Fix admin-classes-view to use Select for school/grade

Profile/Settings: Add loading/error; Fix parent role routing; Create ParentSettingsView; Integrate AiProviderSettingsCard; Add Tab URL persistence; Add logout confirm; Add avatar; Fix Progress arbitrary class

Schema: Add senderDeletedAt/receiverDeletedAt to messages; Add quietHours to notificationPreferences; Add uniqueIndex import

Docs: Update architecture docs 004/005

src/app/(dashboard)/admin/announcements/page.tsx

@@ -1,8 +1,11 @@
 import type { Metadata } from "next"
 import type { JSX } from "react"
 
+import { requirePermission } from "@/shared/lib/auth-guard"
+import { Permissions } from "@/shared/types/permissions"
 import { getAnnouncements } from "@/modules/announcements/data-access"
 import { getGrades } from "@/modules/school/data-access"
+import { getAdminClasses } from "@/modules/classes/data-access"
 import { AdminAnnouncementsView } from "@/modules/announcements/components/admin-announcements-view"
 import { getSearchParam, type SearchParams } from "@/shared/lib/utils"
 import type { AnnouncementStatus } from "@/modules/announcements/types"
@@ -22,19 +25,22 @@ export default async function AdminAnnouncementsPage({
 }: {
   searchParams: Promise<SearchParams>
 }): Promise<JSX.Element> {
+  await requirePermission(Permissions.ANNOUNCEMENT_MANAGE)
   const sp = await searchParams
   const statusParam = getSearchParam(sp, "status")
   const status = isValidStatus(statusParam) ? statusParam : undefined
 
-  const [announcements, grades] = await Promise.all([
+  const [announcements, grades, classes] = await Promise.all([
     getAnnouncements({ status }),
     getGrades(),
+    getAdminClasses(),
   ])
 
   return (
     <AdminAnnouncementsView
       announcements={announcements}
       grades={grades.map((g) => ({ id: g.id, name: g.name }))}
+      classes={classes.map((c) => ({ id: c.id, name: c.name }))}
       initialStatus={status}
     />
   )