feat(parent-portal): 完成参考项目(CICD)家长端功能全量覆盖 - 9 新页面 + 3 页面增强 + 763 测试通过

## 变更内容

### P0 高优先级新页面
- /parent/leave: 请假表单(react-hook-form + Zod) + 历史列表(状态筛选)
- /parent/grades/report-card: 报告卡(学年/学期筛选 + 打印 + 教师评语)
- /parent/children/[studentId]: 子女详情聚合页(5 Tab: overview/homework/grades/exams/schedule)

### P1 中优先级新页面
- /parent/error-book: 错题本(5 项统计 + Top 错题 + 薄弱知识点)
- /parent/diagnostic: 诊断报告(掌握度摘要 + 已发布诊断报告)
- /parent/practice: 练习统计(4 项统计 + 练习历史)

### P2 低优先级新页面
- /parent/course-plans + [id]: 课程计划列表 + 详情(章节列表)
- /parent/lesson-plans + [planId]/view: 备课列表(学科筛选) + 只读详情
- /parent/elective: 选修课(分类色点 + 状态徽标)

### P3 现有页面增强
- /parent/dashboard: ParentAttentionBanner + 多子女卡片网格 + 趋势图标 + 逾期高亮
- /parent/attendance: AttendanceRateCard + AttendanceWarningBanner + 月份导航
- /parent/grades: GrowthArchiveChart + ExportGradesButton + 班级均对比线

### 基础设施
- types/index.ts: +20 新类型(LeaveRequest/ReportCard/ErrorBookStats/DiagnosticReport/PracticeStats/CoursePlan/LessonPlan/ElectiveSelection/ChildDetail/ScheduleItem 等)
- operations.ts: +19 GraphQL operations(17 query + 2 mutation)
- fixtures.ts: +18 mock 数据集
- handlers.ts: +19 MSW GraphQL handler

### 质量校验
- typecheck: 0 错误
- lint: 0 错误
- test: 71 文件 / 763 测试全部通过(从 413 增至 763, +350 测试)

### 文档
- workline.md: 新增 §7 参考项目(CICD)差距分析与实现安排 + §7.3-7.5 实现进度与覆盖完成度

### 设计决策
- 保留当前"单子女切换"范式(MultiChildTabBar + useChildSwitcher),不迁移到"多子女同屏对比"
- 仪表盘除外:已增强为多子女卡片网格并列展示
- 参考项目所有 11 个家长端页面功能已 100% 覆盖

Refs: ARB-020 §22, ARB-022 §24.4

apps/parent-portal/src/app/parent/attendance/page.tsx

@@ -1,16 +1,35 @@
 // 考勤页面
 // 依据：02-architecture-design.md §3.1 路由结构
 // 路由：/parent/attendance
+// - 月份导航（前一月/后一月切换）
+// - 聚合出勤率卡片 + 异常预警横幅
+// - 月度考勤日历
 
 "use client";
 
+import { useState, useMemo } from "react";
 import { useChildAttendance } from "@/hooks/useChildAttendance";
 import { useChildSwitcher } from "@/hooks/useChildSwitcher";
 import { AttendanceCalendar } from "@/components/AttendanceCalendar";
+import { AttendanceRateCard } from "@/components/AttendanceRateCard";
+import { AttendanceWarningBanner } from "@/components/AttendanceWarningBanner";
+
+function getCurrentMonth(): string {
+  const now = new Date();
+  return `${now.getFullYear()}-${String(now.getMonth() + 1).padStart(2, "0")}`;
+}
 
 export default function AttendancePage() {
   const { currentChild } = useChildSwitcher();
-  const { attendance, loading, error } = useChildAttendance();
+  const [currentMonth, setCurrentMonth] = useState<string>(getCurrentMonth);
+  const { attendance, loading, error } = useChildAttendance({
+    month: currentMonth,
+  });
+
+  const monthLabel = useMemo(() => {
+    const [year, month] = currentMonth.split("-");
+    return `${year ?? ""}年${parseInt(month ?? "1", 10)}月`;
+  }, [currentMonth]);
 
   if (loading) {
     return <span className="skeleton h-64 w-full rounded" />;
@@ -27,7 +46,20 @@ export default function AttendancePage() {
   return (
     <div className="space-y-6">
       <h1 className="font-serif text-2xl">{currentChild?.name}的考勤</h1>
-      <AttendanceCalendar records={attendance} />
+
+      <AttendanceRateCard records={attendance} />
+
+      <AttendanceWarningBanner records={attendance} />
+
+      <AttendanceCalendar
+        records={attendance}
+        month={currentMonth}
+        onMonthChange={setCurrentMonth}
+      />
+
+      <p className="text-xs text-ink-muted">
+        当前查看：{monthLabel}
+      </p>
     </div>
   );
 }