feat(app): add error/loading boundaries across all dashboard routes and new routes

- Add error.tsx and loading.tsx boundaries for admin, parent, student, teacher routes

- Add admin announcements edit, audit-logs overview, curriculum-map, invitation-codes, permissions, questions, roles routes

- Add admin elective detail and components, files, course-plans, users, scheduling boundaries

- Add messages group-compose route

- Add parent course-plans, elective, grades report-card, practice routes

- Add student course-plans, elective detail, error-book dialogs, grades report-card, learning study-path, leave, schedule boundaries

- Add teacher attendance report, classes boundaries, course-plans boundaries, elective, exams analytics/edit-rich/all/create/new, grades report-card, homework boundaries, leave, lesson-plans calendar

- Add auth loading, onboarding loading, api cron

src/app/(dashboard)/teacher/textbooks/[id]/loading.tsx

@@ -1,63 +1,46 @@
 import { Skeleton } from "@/shared/components/ui/skeleton"
-import { Separator } from "@/shared/components/ui/separator"
 
 export default function Loading() {
   return (
-    <div className="space-y-6 max-w-5xl mx-auto">
-      {/* Header Skeleton */}
-      <div className="flex items-center gap-4">
-        <Skeleton className="h-10 w-10 rounded-md" /> {/* Back Button */}
-        <div className="flex-1 space-y-2">
+    <div
+      role="status"
+      aria-busy="true"
+      aria-label="加载中"
+      className="flex h-[calc(100vh-4rem)] flex-col overflow-hidden bg-muted/5"
+    >
+      {/* Reader Header Skeleton */}
+      <div className="flex items-center justify-between border-b bg-background/95 backdrop-blur py-3 px-6 shrink-0">
+        <div className="flex items-center gap-3 min-w-0">
+          <Skeleton className="h-6 w-48" />
           <div className="flex items-center gap-2">
-            <Skeleton className="h-5 w-16" />
-            <Skeleton className="h-4 w-24" />
+            <Skeleton className="h-5 w-16 rounded-full" />
+            <Skeleton className="h-5 w-16 rounded-full" />
           </div>
-          <Skeleton className="h-8 w-64" />
         </div>
-        <Skeleton className="h-10 w-32" /> {/* Edit Button */}
       </div>
 
-      <div className="grid grid-cols-1 md:grid-cols-3 gap-8">
-        {/* Main Content Skeleton */}
-        <div className="md:col-span-2 space-y-6">
-          <div className="flex items-center justify-between">
-            <Skeleton className="h-6 w-40" />
-            <Skeleton className="h-8 w-24" />
-          </div>
-
-          <div className="rounded-lg border bg-card p-6 space-y-4">
-            {Array.from({ length: 5 }).map((_, i) => (
-              <div key={i} className="flex items-center gap-4">
-                <Skeleton className="h-6 w-6 rounded-md" />
-                <Skeleton className="h-6 w-full rounded-md" />
+      {/* Reader Body Skeleton: sidebar + content */}
+      <div className="flex-1 overflow-hidden">
+        <div className="h-full max-w-[1600px] mx-auto w-full grid grid-cols-1 md:grid-cols-[280px_1fr]">
+          {/* Chapter Sidebar Skeleton */}
+          <div className="hidden md:block border-r bg-card p-4 space-y-2 overflow-hidden">
+            {Array.from({ length: 8 }).map((_, i) => (
+              <div key={i} className="flex items-center gap-2">
+                <Skeleton className="h-4 w-4 rounded-sm" />
+                <Skeleton className="h-6 w-full" />
               </div>
             ))}
           </div>
-        </div>
 
-        {/* Sidebar Skeleton */}
-        <div className="space-y-6">
-          <div className="rounded-lg border bg-card p-6 space-y-4">
-            <Skeleton className="h-6 w-32 mb-4" />
-            <div className="space-y-2">
-              <Skeleton className="h-4 w-16" />
-              <Skeleton className="h-5 w-32" />
-            </div>
-            <div className="space-y-2">
-              <Skeleton className="h-4 w-20" />
-              <Skeleton className="h-20 w-full" />
-            </div>
-            <Separator />
-            <div className="grid grid-cols-2 gap-4">
-              <div className="space-y-2">
-                <Skeleton className="h-3 w-12" />
-                <Skeleton className="h-4 w-24" />
-              </div>
-              <div className="space-y-2">
-                <Skeleton className="h-3 w-12" />
-                <Skeleton className="h-4 w-24" />
-              </div>
+          {/* Content Area Skeleton */}
+          <div className="p-6 space-y-4 overflow-hidden">
+            <Skeleton className="h-8 w-1/3" />
+            <div className="space-y-3">
+              {Array.from({ length: 6 }).map((_, i) => (
+                <Skeleton key={i} className="h-4 w-full" />
+              ))}
             </div>
+            <Skeleton className="h-32 w-full" />
           </div>
         </div>
       </div>