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-warning.tsx

@@ -0,0 +1,115 @@
+"use client"
+
+import { AlertTriangle, Phone } 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 Warning = {
+  studentId: string
+  studentName: string
+  message: string
+  severity: "high" | "medium"
+}
+
+/** 翻译函数类型（与 `useTranslations("attendance")` 返回值兼容） */
+type Translator = ReturnType<typeof useTranslations>
+
+/**
+ * 构建考勤异常预警列表（纯函数，便于测试）。
+ */
+export function buildWarnings(
+  summaries: ParentStudentAttendanceSummary[],
+  t: Translator,
+): Warning[] {
+  const warnings: Warning[] = []
+
+  for (const s of summaries) {
+    const { stats, studentName, studentId } = s
+    if (stats.absent >= 3) {
+      warnings.push({
+        studentId,
+        studentName,
+        message: t("parent.absentHighSeverity", { count: stats.absent }),
+        severity: "high",
+      })
+    } else if (stats.absent >= 1) {
+      warnings.push({
+        studentId,
+        studentName,
+        message: t("parent.absentWarning", { count: stats.absent }),
+        severity: "medium",
+      })
+    }
+
+    if (stats.late >= 3) {
+      warnings.push({
+        studentId,
+        studentName,
+        message: t("parent.lateWarning", { count: stats.late }),
+        severity: "medium",
+      })
+    }
+
+    if (stats.presentRate < 90 && stats.total > 0) {
+      warnings.push({
+        studentId,
+        studentName,
+        message: t("parent.lowRateWarning", { rate: stats.presentRate.toFixed(1) }),
+        severity: "high",
+      })
+    }
+  }
+
+  return warnings
+}
+
+/**
+ * 家长视角的考勤异常预警横幅。
+ * 聚合所有子女的考勤异常（缺勤、迟到、低出勤率），提醒家长及时关注。
+ */
+export function ParentAttendanceWarning({
+  summaries,
+}: {
+  summaries: ParentStudentAttendanceSummary[]
+}) {
+  const t = useTranslations("attendance")
+  const warnings = buildWarnings(summaries, t)
+  if (warnings.length === 0) return null
+
+  return (
+    <Card
+      className={cn(
+        "border-destructive/30 bg-destructive/5 p-4",
+        warnings.some((w) => w.severity === "high") && "border-destructive/50",
+      )}
+      aria-label={t("parent.warningTitle")}
+    >
+      <div className="flex items-start gap-3">
+        <AlertTriangle
+          className="h-5 w-5 text-destructive shrink-0 mt-0.5"
+          aria-hidden
+        />
+        <div className="flex-1 space-y-2">
+          <div className="text-sm font-semibold text-destructive">
+            {t("parent.warningTitle")}
+          </div>
+          <ul className="space-y-1.5 text-sm">
+            {warnings.map((w, idx) => (
+              <li key={`${w.studentId}-${idx}`} className="flex items-start gap-2">
+                <span className="font-medium shrink-0">{w.studentName}:</span>
+                <span className="text-muted-foreground">{w.message}</span>
+              </li>
+            ))}
+          </ul>
+          <div className="flex items-center gap-2 pt-1 text-xs text-muted-foreground">
+            <Phone className="h-3 w-3" aria-hidden />
+            <span>{t("parent.contactHomeroom")}</span>
+          </div>
+        </div>
+      </div>
+    </Card>
+  )
+}