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/modules/dashboard/components/student-dashboard/student-stats-grid.tsx

@@ -1,11 +1,13 @@
-import { PenTool, TriangleAlert, Trophy, TrendingUp } from "lucide-react"
+import { BookOpen, CheckCircle, PenTool, TriangleAlert, Trophy, TrendingUp } from "lucide-react"
 
 import { StatCard } from "@/shared/components/ui/stat-card"
 import type { StudentRanking } from "@/modules/homework/types"
 
 export function StudentStatsGrid({
+  enrolledClassCount,
   dueSoonCount,
   overdueCount,
+  gradedCount,
   ranking,
 }: {
   enrolledClassCount: number
@@ -16,12 +18,21 @@ export function StudentStatsGrid({
 }) {
   return (
     <div className="grid gap-4 md:grid-cols-2 lg:grid-cols-4">
+      <StatCard
+        title="Enrolled Classes"
+        value={String(enrolledClassCount)}
+        description="Active enrollments"
+        icon={BookOpen}
+        href="/student/learning/courses"
+        color="text-emerald-500"
+        valueClassName="text-emerald-500 tabular-nums"
+      />
       <StatCard
         title="Average Score"
         value={ranking ? `${Math.round(ranking.percentage)}%` : "-"}
         description={ranking ? "Overall performance" : "No grades yet"}
         icon={TrendingUp}
-        href="/student/learning/assignments"
+        href="/student/grades"
         color="text-blue-500"
         valueClassName={ranking ? "text-blue-500 tabular-nums" : "tabular-nums"}
       />
@@ -30,10 +41,19 @@ export function StudentStatsGrid({
         value={ranking ? `${ranking.rank}/${ranking.classSize}` : "-"}
         description={ranking ? "Current position" : "No ranking yet"}
         icon={Trophy}
-        href="/student/learning/assignments"
+        href="/student/grades"
         color="text-purple-500"
         valueClassName={ranking ? "text-purple-500 tabular-nums" : "tabular-nums"}
       />
+      <StatCard
+        title="Graded"
+        value={String(gradedCount)}
+        description="Completed assignments"
+        icon={CheckCircle}
+        href="/student/learning/assignments"
+        color="text-green-500"
+        valueClassName="text-green-500 tabular-nums"
+      />
       <StatCard
         title="Due Soon"
         value={String(dueSoonCount)}