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)/student/learning/assignments/page.tsx

@@ -6,6 +6,7 @@ import { Button } from "@/shared/components/ui/button"
 import { Card, CardContent, CardHeader, CardTitle } from "@/shared/components/ui/card"
 import { StatusBadge } from "@/shared/components/ui/status-badge"
 import { formatDate, cn } from "@/shared/lib/utils"
+import { getParam, type SearchParams } from "@/shared/lib/search-params"
 import { getStudentHomeworkAssignments } from "@/modules/homework/data-access"
 import { getCurrentStudentUser } from "@/modules/users/data-access"
 import { AssignmentFilters } from "@/modules/homework/components/assignment-filters"
@@ -20,13 +21,6 @@ import {
 
 export const dynamic = "force-dynamic"
 
-type SearchParams = { [key: string]: string | string[] | undefined }
-
-const getParam = (params: SearchParams, key: string) => {
-  const v = params[key]
-  return Array.isArray(v) ? v[0] : v
-}
-
 const getActionLabel = (status: StudentHomeworkProgressStatus, t: (key: string) => string): string => {
   switch (status) {
     case "graded":