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-graph.tsx

@@ -66,7 +66,6 @@ function KnowledgeGraphInner({ textbookId, initialViewMode = "structure" }: Know
   const t = useTranslations("textbooks")
   const { hasPermission } = usePermission()
   const canEdit = hasPermission(Permissions.TEXTBOOK_UPDATE)
-  const isTeacher = hasPermission(Permissions.TEXTBOOK_UPDATE)
   const reactFlow = useReactFlow()
 
   const [viewMode, setViewMode] = useState<GraphViewMode>(initialViewMode)
@@ -77,9 +76,10 @@ function KnowledgeGraphInner({ textbookId, initialViewMode = "structure" }: Know
   const [newPrereqId, setNewPrereqId] = useState<string>("")
   const [isSavingPrereq, setIsSavingPrereq] = useState(false)
 
-  const { data, isLoading, error, reload } = useGraphData(textbookId, viewMode)
+  const { data, isLoading, isRefreshing, error, reload } = useGraphData(textbookId, viewMode)
 
-  const availableViewModes: GraphViewMode[] = isTeacher
+  // 教师可查看班级掌握度，学生可查看个人掌握度
+  const availableViewModes: GraphViewMode[] = canEdit
     ? ["structure", "class-mastery"]
     : ["structure", "student-mastery"]
 
@@ -286,6 +286,7 @@ function KnowledgeGraphInner({ textbookId, initialViewMode = "structure" }: Know
           searchText={searchText}
           onSearchChange={setSearchText}
           onResetView={resetView}
+          isRefreshing={isRefreshing}
         />
         <div className="flex-1 min-h-0 relative">
           <ReactFlow
@@ -315,6 +316,7 @@ function KnowledgeGraphInner({ textbookId, initialViewMode = "structure" }: Know
       </div>
 
       {selectedKp && (
+        // 任意值 w-[300px]：详情面板固定宽度，保证内容可读性
         <div className="w-[300px] shrink-0">
           <GraphNodeDetailPanel
             kp={selectedKp}
@@ -322,7 +324,6 @@ function KnowledgeGraphInner({ textbookId, initialViewMode = "structure" }: Know
             prerequisites={prerequisites}
             successors={successors}
             canEdit={canEdit}
-            textbookId={textbookId}
             onClose={() => setSelectedKpId(null)}
             onJumpToKp={onJumpToKp}
             onAddPrerequisite={() => setAddPrereqOpen(true)}