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/questions/page.tsx

@@ -10,6 +10,8 @@ import { EmptyState } from "@/shared/components/ui/empty-state"
 import { Skeleton } from "@/shared/components/ui/skeleton"
 import { getQuestions } from "@/modules/questions/data-access"
 import { getParam, type SearchParams } from "@/shared/lib/search-params"
+import { requirePermission } from "@/shared/lib/auth-guard"
+import { Permissions } from "@/shared/types/permissions"
 import type { QuestionType } from "@/modules/questions/types"
 
 export const dynamic = "force-dynamic"
@@ -27,6 +29,8 @@ function parseQuestionType(v?: string): QuestionType | undefined {
 }
 
 async function QuestionBankResults({ searchParams }: { searchParams: Promise<SearchParams> }): Promise<JSX.Element> {
+  await requirePermission(Permissions.QUESTION_READ)
+
   const params = await searchParams
 
   const q = getParam(params, "q")
@@ -36,10 +40,13 @@ async function QuestionBankResults({ searchParams }: { searchParams: Promise<Sea
 
   const questionType = parseQuestionType(type)
 
+  const difficultyNum = difficulty && difficulty !== "all" ? Number(difficulty) : undefined
+  const safeDifficulty = difficultyNum !== undefined && Number.isFinite(difficultyNum) ? difficultyNum : undefined
+
   const { data: questions } = await getQuestions({
     q: q || undefined,
     type: questionType,
-    difficulty: difficulty && difficulty !== "all" ? Number(difficulty) : undefined,
+    difficulty: safeDifficulty,
     knowledgePointId: knowledgePointId && knowledgePointId !== "all" ? knowledgePointId : undefined,
     pageSize: 200,
   })