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/[assignmentId]/page.tsx

@@ -24,7 +24,7 @@ export default async function StudentAssignmentTakePage({
   const status = data.submission?.status
   if (status === "graded" || status === "submitted") {
     return (
-      <div className="h-full flex-1 flex-col space-y-8 p-8 md:flex">
+      <div className="space-y-8">
         <div className="flex flex-col gap-1">
           <h2 className="text-2xl font-bold tracking-tight">{data.assignment.title}</h2>
           <div className="text-sm text-muted-foreground">
@@ -38,7 +38,7 @@ export default async function StudentAssignmentTakePage({
   }
 
   return (
-    <div className="flex h-full flex-col space-y-4 p-6">
+    <div className="space-y-4">
       <div className="flex flex-col gap-1">
         <h2 className="text-2xl font-bold tracking-tight">{data.assignment.title}</h2>
         <div className="text-sm text-muted-foreground">