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)/teacher/course-plans/[id]/page.tsx

@@ -1,6 +1,8 @@
 import type { JSX } from "react"
 import { notFound } from "next/navigation"
 
+import { requirePermission } from "@/shared/lib/auth-guard"
+import { Permissions } from "@/shared/types/permissions"
 import { getCoursePlanById } from "@/modules/course-plans/data-access"
 import { CoursePlanDetail } from "@/modules/course-plans/components/course-plan-detail"
 
@@ -11,6 +13,7 @@ export default async function TeacherCoursePlanDetailPage({
 }: {
   params: Promise<{ id: string }>
 }): Promise<JSX.Element> {
+  await requirePermission(Permissions.COURSE_PLAN_READ)
   const { id } = await params
   const plan = await getCoursePlanById(id)