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/page.tsx

@@ -1,5 +1,6 @@
 import type { JSX } from "react"
-import { getAuthContext } from "@/shared/lib/auth-guard"
+import { requirePermission } from "@/shared/lib/auth-guard"
+import { Permissions } from "@/shared/types/permissions"
 import { getParam, type SearchParams } from "@/shared/lib/search-params"
 import { getCoursePlans } from "@/modules/course-plans/data-access"
 import { CoursePlanList } from "@/modules/course-plans/components/course-plan-list"
@@ -23,7 +24,7 @@ export default async function TeacherCoursePlansPage({
 }: {
   searchParams: Promise<SearchParams>
 }): Promise<JSX.Element> {
-  const ctx = await getAuthContext()
+  const ctx = await requirePermission(Permissions.COURSE_PLAN_READ)
   const teacherId = ctx.userId
 
   const sp = await searchParams