refactor(attendance,elective): 审计第二轮 — 全量完成 P0/P1 改进项

P0 修复：
- 页面层 i18n 全量补齐（admin/teacher/parent/student × attendance/elective）
- types.ts 状态标签常量迁移至 constants.ts（i18n key + Badge variant）
- 修复 getTranslations 导入路径（next-intl → next-intl/server）

P1 改进：
- 解耦 parent 模块对 attendance 类型的直接依赖（本地 view-model 类型）
- 导出纯函数（computeStats/buildWarnings/buildLotteryRankCase 等）
- 统一空状态为 EmptyState 组件
- 清理死代码读 Action（attendance 5 个 + elective 3 个）
- 预留监控埋点接口（trackEvent 13 个新事件名）
- 补齐骨架屏 loading.tsx（8 个页面）
- AlertDialog 替换 window.confirm（student-selection-view）
- a11y 改进（aria-label/role/键盘导航）

修复：
- AttendanceStatus 从 constants.ts 重导出，消除 types/constants 双源混乱
- buildWarnings 的 Translator 类型改用 ReturnType<typeof useTranslations>

src/modules/parent/components/parent-attendance-rate-card.tsx

@@ -0,0 +1,130 @@
+"use client"
+
+import { CalendarCheck, CalendarX, Clock, TrendingUp } from "lucide-react"
+import { useTranslations } from "next-intl"
+
+import { Card } from "@/shared/components/ui/card"
+import { cn } from "@/shared/lib/utils"
+import type { ParentStudentAttendanceSummary } from "@/modules/parent/types"
+
+type AggregateStats = {
+  totalStudents: number
+  avgPresentRate: number
+  totalAbsent: number
+  totalLate: number
+}
+
+/**
+ * 聚合多个子女的考勤统计（纯函数，便于测试）。
+ */
+export function aggregateStats(
+  summaries: ParentStudentAttendanceSummary[],
+): AggregateStats {
+  if (summaries.length === 0) {
+    return { totalStudents: 0, avgPresentRate: 0, totalAbsent: 0, totalLate: 0 }
+  }
+  const totalStudents = summaries.length
+  const sumRate = summaries.reduce(
+    (sum, s) => sum + (s.stats.total > 0 ? s.stats.presentRate : 0),
+    0,
+  )
+  const avgPresentRate = sumRate / totalStudents
+  const totalAbsent = summaries.reduce((sum, s) => sum + s.stats.absent, 0)
+  const totalLate = summaries.reduce((sum, s) => sum + s.stats.late, 0)
+  return { totalStudents, avgPresentRate, totalLate, totalAbsent }
+}
+
+/**
+ * 根据出勤率返回语气色调（纯函数，便于测试）。
+ */
+export function rateTone(rate: number): "good" | "warn" | "bad" {
+  if (rate >= 95) return "good"
+  if (rate >= 90) return "warn"
+  return "bad"
+}
+
+const TONE_STYLES: Record<"good" | "warn" | "bad", string> = {
+  good: "text-emerald-600",
+  warn: "text-amber-600",
+  bad: "text-destructive",
+}
+
+/**
+ * 家长考勤页顶部的出勤率汇总卡片。
+ * 聚合所有子女的出勤率、缺勤、迟到总数，让家长一眼掌握整体情况。
+ */
+export function ParentAttendanceRateCard({
+  summaries,
+}: {
+  summaries: ParentStudentAttendanceSummary[]
+}) {
+  const t = useTranslations("attendance")
+  const stats = aggregateStats(summaries)
+  if (stats.totalStudents === 0) return null
+
+  const tone = rateTone(stats.avgPresentRate)
+  const rateLabel =
+    stats.avgPresentRate >= 95
+      ? t("parent.rateExcellent")
+      : stats.avgPresentRate >= 90
+        ? t("parent.rateNeedsAttention")
+        : t("parent.rateBelowStandard")
+
+  return (
+    <Card className="p-4" aria-label={t("parent.rateCardTitle")}>
+      <div className="grid grid-cols-2 gap-3 sm:grid-cols-4">
+        <div className="space-y-1">
+          <div className="flex items-center gap-1 text-xs text-muted-foreground">
+            <TrendingUp className="h-3 w-3" aria-hidden />
+            {t("stats.attendanceRate")}
+          </div>
+          <div className={cn("text-2xl font-bold tabular-nums", TONE_STYLES[tone])}>
+            {stats.avgPresentRate.toFixed(1)}%
+          </div>
+          <div className="text-xs text-muted-foreground">{rateLabel}</div>
+        </div>
+
+        <div className="space-y-1">
+          <div className="flex items-center gap-1 text-xs text-muted-foreground">
+            <CalendarCheck className="h-3 w-3" aria-hidden />
+            {t("parent.children")}
+          </div>
+          <div className="text-2xl font-bold tabular-nums">{stats.totalStudents}</div>
+          <div className="text-xs text-muted-foreground">{t("parent.linked")}</div>
+        </div>
+
+        <div className="space-y-1">
+          <div className="flex items-center gap-1 text-xs text-muted-foreground">
+            <CalendarX className="h-3 w-3" aria-hidden />
+            {t("stats.absent")}
+          </div>
+          <div
+            className={cn(
+              "text-2xl font-bold tabular-nums",
+              stats.totalAbsent > 0 && "text-destructive",
+            )}
+          >
+            {stats.totalAbsent}
+          </div>
+          <div className="text-xs text-muted-foreground">{t("parent.thisPeriod")}</div>
+        </div>
+
+        <div className="space-y-1">
+          <div className="flex items-center gap-1 text-xs text-muted-foreground">
+            <Clock className="h-3 w-3" aria-hidden />
+            {t("stats.late")}
+          </div>
+          <div
+            className={cn(
+              "text-2xl font-bold tabular-nums",
+              stats.totalLate > 0 && "text-amber-600",
+            )}
+          >
+            {stats.totalLate}
+          </div>
+          <div className="text-xs text-muted-foreground">{t("parent.thisPeriod")}</div>
+        </div>
+      </div>
+    </Card>
+  )
+}