feat(attendance,elective): 实现所有 P2 长期改进项

P2 修复（来自审计报告）：
- 2.4.4: Server Action 错误消息 i18n 化（attendance/elective 全部 Action）
- 2.5.3: 抽取 AttendancePageLayout 组件复用（admin/teacher 页面）
- 2.5.4: 抽取 ElectivePageLayout 组件复用（admin/teacher 列表页）
- 2.6.3: 考勤月历键盘导航（tabIndex + 方向键 + Home/End + role=grid）
- 2.8.2: getStudentAttendanceSummary 分页优化（SQL 聚合统计 + LIMIT 分页）
- 2.8.3: resolveCourseDisplayNames 缓存优化（React cache 去重）
- 2.1.4: elective data-access 跨模块依赖接口抽象（resolvers.ts 可注入）

P2 建议项：
- 选课时间冲突检测（parseSchedule + isScheduleConflict 纯函数 + checkScheduleConflict）
- 学分上限校验（MAX_CREDIT_PER_TERM + checkCreditLimit）
- 考勤/选课数据导出 Excel（export.ts + API 路由扩展）

新增文件：
- src/modules/attendance/components/attendance-page-layout.tsx
- src/modules/elective/components/elective-page-layout.tsx
- src/modules/elective/resolvers.ts
- src/modules/attendance/export.ts
- src/modules/elective/export.ts

校验：
- npm run lint 通过（exit 0）
- npx tsc --noEmit attendance/elective/parent 相关零错误

src/modules/textbooks/components/knowledge-point-list.tsx

@@ -1,6 +1,6 @@
 "use client"
 
-import { PlusCircle, Pencil, Trash2 } from "lucide-react"
+import { PlusCircle, Pencil, Trash2, Tag } from "lucide-react"
 import { useTranslations } from "next-intl"
 
 import type { KnowledgePoint } from "../types"
@@ -8,6 +8,7 @@ import { cn } from "@/shared/lib/utils"
 import { ScrollArea } from "@/shared/components/ui/scroll-area"
 import { Badge } from "@/shared/components/ui/badge"
 import { Button } from "@/shared/components/ui/button"
+import { EmptyState } from "@/shared/components/ui/empty-state"
 
 interface KnowledgePointListProps {
   knowledgePoints: KnowledgePoint[]
@@ -35,9 +36,12 @@ export function KnowledgePointList({
 
   if (knowledgePoints.length === 0) {
     return (
-      <div className="flex h-full items-center justify-center text-muted-foreground p-4 text-center text-sm">
-        {t("reader.emptyKnowledge")}
-      </div>
+      <EmptyState
+        icon={Tag}
+        title={t("reader.emptyKnowledge")}
+        description={t("reader.emptyKnowledgeDesc")}
+        className="h-full border-none shadow-none bg-transparent"
+      />
     )
   }
 
@@ -57,6 +61,7 @@ export function KnowledgePointList({
             <div className="flex items-start justify-between gap-2">
               <h4 className="text-sm font-medium leading-none">{kp.name}</h4>
               <div className="flex items-center gap-1">
+                {/* 任意值 text-[10px]：紧凑徽章，text-xs(12px) 在列表项中过大 */}
                 <Badge variant="outline" className="text-[10px] h-5 px-1">
                   {t("panel.level")}
                   {kp.level}