feat: 支持单套试卷同一提交人多次刷卷并展示

- DataService::build 新增 aggregateByStudent 按学号聚合：
  dedupe=true 仅保留最新一份；false 则每学号一行（代表成绩取最高分）
  附 attempts(次数) 与 attempts_list(每次提交明细)，修正提交人数被多次提交inflate的问题
- api.php dashboard 透传 attempts/attempts_list；statOf 增加 attempts 求和；export 增加刷题次数列
- dashboard.php 成员榜加"刷N次"徽标，点击下钻弹窗看每次提交（时间/成绩/时长/暂存）；hero 显示总提交次数
- 主统计页成绩明细同样加"刷N次"徽标与下钻弹窗
- stats 新增 attempts_total

api.php

@@ -217,6 +217,7 @@ try {
             $statOf = static function (array $stu, array $rs, int $fs): array {
                 $total     = count($stu);
                 $submitted = count($rs);
+                $attempts  = array_sum(array_map(static fn($r) => (int)($r['attempts'] ?? 1), $rs));
                 $scores    = array_values(array_filter(array_map(static fn($r) => $r['score'] ?? null, $rs), static fn($v) => $v !== null));
                 $avg       = $scores !== [] ? round(array_sum($scores) / count($scores), 2) : null;
                 $pass      = count(array_filter($rs, static fn($r) => ($r['score'] ?? null) !== null && ($r['score'] >= 0.6 * $fs)));
@@ -226,6 +227,7 @@ try {
                 return [
                     'total'        => $total,
                     'submitted'    => $submitted,
+                    'attempts'     => $attempts,
                     'absent'       => max(0, $total - $submitted),
                     'rate'         => $total > 0 ? round($submitted / $total * 100, 1) : 0,
                     'avg'          => $avg,
@@ -237,13 +239,16 @@ try {
             };
 
             // 已提交成员榜：按成绩从高到低，缺成绩者排最后，并给出排名
+            // 透传 attempts / attempts_list，供前端展示"同人多刷卷"
             $membersOf = static function (array $rs): array {
                 $ms = [];
                 foreach ($rs as $r) {
                     $ms[] = [
-                        'sid'   => (string)($r['sid'] ?? ''),
-                        'name'  => (string)($r['name'] ?? ''),
-                        'score' => ($r['score'] ?? null),
+                        'sid'           => (string)($r['sid'] ?? ''),
+                        'name'          => (string)($r['name'] ?? ''),
+                        'score'         => ($r['score'] ?? null),
+                        'attempts'      => (int)($r['attempts'] ?? 1),
+                        'attempts_list' => $r['attempts_list'] ?? [],
                     ];
                 }
                 usort($ms, static function (array $a, array $b): int {
@@ -440,7 +445,7 @@ try {
                     fputcsv($out, [$r['sid'] ?? '', $r['name'] ?? '', $r['cls'] ?? '', $r['grp'] ?? '']);
                 }
             } else {
-                fputcsv($out, ['学号', '姓名', '班级', '组别', '成绩', '提交时间', '考试时长', '考试时长(秒)']);
+                fputcsv($out, ['学号', '姓名', '班级', '组别', '成绩', '提交时间', '考试时长', '考试时长(秒)', '刷题次数']);
                 foreach ($rows as $r) {
                     fputcsv($out, [
                         $r['sid'] ?? '',
@@ -451,6 +456,7 @@ try {
                         $r['submit_at'] ?? '',
                         $r['duration_txt'] ?? '',
                         $r['duration'] === null ? '' : $r['duration'],
+                        (int)($r['attempts'] ?? 1),
                     ]);
                 }
             }