feat(app): add error/loading boundaries and update dashboard routes

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

- Add dashboard-error-fallback and dashboard-loading-skeleton components

- Add student/learning page, parent/leave routes, teacher textbook components

- Update existing app routes across auth, dashboard, and API endpoints

- Update proxy middleware and next-auth type declarations

src/app/(dashboard)/parent/error.tsx

@@ -0,0 +1,23 @@
+"use client"
+
+import { EmptyState } from "@/shared/components/ui/empty-state"
+import { AlertTriangle } from "lucide-react"
+
+export default function ParentError({
+  error,
+  reset,
+}: {
+  error: Error & { digest?: string }
+  reset: () => void
+}) {
+  return (
+    <div className="p-6 md:p-8">
+      <EmptyState
+        icon={AlertTriangle}
+        title="Something went wrong"
+        description={error.message || "An unexpected error occurred. Please try again."}
+        action={{ label: "Try again", onClick: reset }}
+      />
+    </div>
+  )
+}