feat(attendance): add correlation, trend, warnings, report print, and services

- Add attendance-grade-correlation-card and data-access-correlation, correlation-compute

- Add attendance-trend-chart and trend-compute for trend analysis

- Add attendance-warnings-card and warning-compute for attendance warnings

- Add attendance-report-print for printable reports

- Add class-comparison-card for class attendance comparison

- Add notifications and services directory

src/modules/attendance/warning-compute.ts

@@ -0,0 +1,152 @@
+import type {
+  AttendanceWarning,
+  AttendanceWarningSeverity,
+  AttendanceWarningSummary,
+} from "./types"
+
+/**
+ * L-3：预警阈值默认值（当班级未配置规则时使用）。
+ */
+export const DEFAULT_ATTENDANCE_RATE_THRESHOLD = 90
+export const DEFAULT_CONSECUTIVE_ABSENCE_THRESHOLD = 3
+
+/**
+ * 出勤率预警的严重等级划分：
+ * - high：低于阈值 10 个百分点以上
+ * - medium：低于阈值 5-10 个百分点
+ * - low：低于阈值 5 个百分点以内
+ */
+const rateSeverity = (current: number, threshold: number): AttendanceWarningSeverity => {
+  const diff = threshold - current
+  if (diff >= 10) return "high"
+  if (diff >= 5) return "medium"
+  return "low"
+}
+
+/**
+ * 连续缺勤预警的严重等级划分：
+ * - high：连续缺勤 ≥ 阈值 + 2
+ * - medium：连续缺勤 ≥ 阈值 + 1
+ * - low：连续缺勤 = 阈值
+ */
+const absenceSeverity = (current: number, threshold: number): AttendanceWarningSeverity => {
+  if (current >= threshold + 2) return "high"
+  if (current >= threshold + 1) return "medium"
+  return "low"
+}
+
+/**
+ * 从按日期升序的状态列表中计算最长连续缺勤段。
+ * 缺勤定义为 status === "absent"（不含 late/early_leave 等其他异常状态）。
+ * 返回 { maxStreak, lastStreakDates }：最长连续段及其日期列表。
+ */
+export const computeConsecutiveAbsence = (
+  records: { date: string; status: string }[]
+): { maxStreak: number; lastStreakDates: string[] } => {
+  if (records.length === 0) return { maxStreak: 0, lastStreakDates: [] }
+
+  // 按日期升序排序
+  const sorted = [...records].sort((a, b) => a.date.localeCompare(b.date))
+  let maxStreak = 0
+  let currentStreak = 0
+  let currentStreakStart = 0
+  let lastMaxStart = 0
+
+  for (let i = 0; i < sorted.length; i++) {
+    if (sorted[i].status === "absent") {
+      if (currentStreak === 0) currentStreakStart = i
+      currentStreak += 1
+      if (currentStreak > maxStreak) {
+        maxStreak = currentStreak
+        lastMaxStart = currentStreakStart
+      }
+    } else {
+      currentStreak = 0
+    }
+  }
+
+  const lastStreakDates = maxStreak > 0
+    ? sorted.slice(lastMaxStart, lastMaxStart + maxStreak).map((r) => r.date)
+    : []
+
+  return { maxStreak, lastStreakDates }
+}
+
+/**
+ * L-3：根据学生出勤率统计和阈值生成预警列表（纯函数，便于测试）。
+ *
+ * @param studentStats 学生列表，每项含 studentId/studentName/total/present 和按日期升序的记录
+ * @param attendanceRateThreshold 出勤率阈值（百分比）
+ * @param consecutiveAbsenceThreshold 连续缺勤阈值（次）
+ */
+export const computeAttendanceWarnings = (
+  studentStats: {
+    studentId: string
+    studentName: string
+    total: number
+    present: number
+    records: { date: string; status: string }[]
+  }[],
+  attendanceRateThreshold: number,
+  consecutiveAbsenceThreshold: number
+): AttendanceWarning[] => {
+  const warnings: AttendanceWarning[] = []
+
+  for (const s of studentStats) {
+    // 跳过无记录的学生（避免除零，且无记录不触发预警）
+    if (s.total === 0) continue
+
+    const presentRate = Math.round((s.present / s.total) * 10000) / 100
+
+    // 出勤率低于阈值
+    if (presentRate < attendanceRateThreshold) {
+      warnings.push({
+        studentId: s.studentId,
+        studentName: s.studentName,
+        type: "low_attendance_rate",
+        severity: rateSeverity(presentRate, attendanceRateThreshold),
+        currentValue: presentRate,
+        threshold: attendanceRateThreshold,
+        relatedDates: [],
+      })
+    }
+
+    // 连续缺勤达到阈值
+    const { maxStreak, lastStreakDates } = computeConsecutiveAbsence(s.records)
+    if (maxStreak >= consecutiveAbsenceThreshold) {
+      warnings.push({
+        studentId: s.studentId,
+        studentName: s.studentName,
+        type: "consecutive_absence",
+        severity: absenceSeverity(maxStreak, consecutiveAbsenceThreshold),
+        currentValue: maxStreak,
+        threshold: consecutiveAbsenceThreshold,
+        relatedDates: lastStreakDates,
+      })
+    }
+  }
+
+  // 严重等级排序：high → medium → low
+  const severityOrder: Record<AttendanceWarningSeverity, number> = {
+    high: 0,
+    medium: 1,
+    low: 2,
+  }
+  warnings.sort((a, b) => severityOrder[a.severity] - severityOrder[b.severity])
+
+  return warnings
+}
+
+/**
+ * 构造空的预警汇总（当班级无数据或无规则时使用）。
+ */
+export const createEmptyWarningSummary = (
+  classId: string,
+  className: string
+): AttendanceWarningSummary => ({
+  classId,
+  className,
+  attendanceRateThreshold: DEFAULT_ATTENDANCE_RATE_THRESHOLD,
+  consecutiveAbsenceThreshold: DEFAULT_CONSECUTIVE_ABSENCE_THRESHOLD,
+  warnings: [],
+})