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/schedule-changes/page.tsx

@@ -2,7 +2,8 @@ import type { JSX } from "react"
 import { ClipboardList } from "lucide-react"
 
 import { EmptyState } from "@/shared/components/ui/empty-state"
-import { getAuthContext } from "@/shared/lib/auth-guard"
+import { requirePermission } from "@/shared/lib/auth-guard"
+import { Permissions } from "@/shared/types/permissions"
 import {
   getAdminClassesForScheduling,
   getScheduleChanges,
@@ -14,10 +15,10 @@ import { ScheduleChangeList } from "@/modules/scheduling/components/schedule-cha
 export const dynamic = "force-dynamic"
 
 export default async function TeacherScheduleChangesPage(): Promise<JSX.Element> {
-  const ctx = await getAuthContext()
+  const ctx = await requirePermission(Permissions.SCHEDULE_ADJUST)
 
   // Teachers see only their own requests; admins landing here see all.
-  const requesterId = ctx.roles.includes("admin") ? undefined : ctx.userId
+  const requesterId = ctx.dataScope.type === "all" ? undefined : ctx.userId
 
   const [classes, teachers, items] = await Promise.all([
     getAdminClassesForScheduling(),