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

lib/DataService.php

@@ -128,9 +128,8 @@ class DataService
         $includeTemp = !empty($cfg['include_temp_save']);
         $dedupe      = !empty($cfg['dedupe']);
 
-        $rows      = [];
+        $rawRows   = [];   // 已匹配学号的原始 row（每条 = 一次提交）
         $unmatched = [];
-        $seenSid   = [];
 
         foreach ($answers as $a) {
             $tempSave = isset($a['tempSave']) ? (int)$a['tempSave'] : 1;
@@ -226,19 +225,15 @@ class DataService
                 continue;
             }
 
-            if ($dedupe && isset($seenSid[$sid])) {
-                $idx = $seenSid[$sid];
-                // 保留提交时间最新的一份
-                if ($ts >= ($rows[$idx]['submit_ts'] ?? 0)) {
-                    $rows[$idx] = $row;
-                    $seenSid[$sid] = $idx;
-                }
-                continue;
-            }
-            $seenSid[$sid] = count($rows);
-            $rows[] = $row;
+            $rawRows[] = $row;
         }
 
+        // 按学号聚合：dedupe=true 仅保留最新一份；false 则每名一行（代表=最高分）
+        // 并附带 attempts(次数) / attempts_list(每次提交明细)，供看板展示"多次刷题"
+        $agg           = self::aggregateByStudent($rawRows, $dedupe);
+        $rows          = $agg['rows'];
+        $attemptsTotal = $agg['attempts_total'];
+
         // 成绩明细默认按提交时间降序（最新在前），学号作为次级排序
         usort($rows, static function (array $x, array $y): int {
             $d = ($y['submit_ts'] ?? 0) <=> ($x['submit_ts'] ?? 0);
@@ -292,6 +287,7 @@ class DataService
             'min_score'     => $scores !== [] ? min($scores) : null,
             'avg_duration'  => $durs !== [] ? (int)round(array_sum($durs) / count($durs)) : null,
             'answer_total'  => count($answers),
+            'attempts_total'=> $attemptsTotal,
         ];
 
         return [
@@ -312,4 +308,68 @@ class DataService
             'updated_at' => date('Y-m-d H:i:s'),
         ];
     }
+
+    /**
+     * 按学号聚合一次提交的答卷记录，解决"同人多次刷卷"在看板中被当成多个人的问题。
+     * - dedupe=true：每学号仅保留提交时间最新的一份（原行为）
+     * - dedupe=false：每学号一行，代表成绩取最高分，附 attempts(次数) / attempts_list(每次提交明细)
+     *
+     * @param array $rows 已匹配学号的原始 row（每条 = 一次提交）
+     * @return array{rows:array, attempts_total:int}
+     */
+    public static function aggregateByStudent(array $rows, bool $dedupe): array
+    {
+        $bySid = [];
+        foreach ($rows as $r) {
+            $bySid[(string)($r['sid'] ?? '')][] = $r;
+        }
+        $agg = [];
+        $attemptsTotal = 0;
+        foreach ($bySid as $sid => $list) {
+            $attemptsTotal += count($list);
+            // 升序：旧 -> 新
+            $sorted = $list;
+            usort($sorted, static function (array $x, array $y): int {
+                return ($x['submit_ts'] ?? 0) <=> ($y['submit_ts'] ?? 0);
+            });
+            $attemptsList = array_map(static function (array $a): array {
+                return [
+                    'submit_at'    => $a['submit_at'],
+                    'submit_ts'    => $a['submit_ts'],
+                    'score'        => $a['score'],
+                    'duration'     => $a['duration'],
+                    'duration_txt' => $a['duration_txt'],
+                    'answer_id'    => $a['answer_id'],
+                    'temp_save'    => $a['temp_save'],
+                ];
+            }, $sorted);
+
+            if ($dedupe) {
+                // 仅保留提交时间最新的一份（明细列表也只留这一份，与"只保留最新"语义一致）
+                $row = $sorted[count($sorted) - 1];
+                $row['attempts']      = 1;
+                $row['best_score']    = $row['score'];
+                $row['attempts_list'] = [$attemptsList[count($attemptsList) - 1]];
+            } else {
+                // 代表成绩取最高分（null 成绩不参与比较，全部为 null 时回退为最近一份）
+                $best = null;
+                $bestScore = null;
+                foreach ($sorted as $a) {
+                    if ($a['score'] !== null && ($bestScore === null || $a['score'] > $bestScore)) {
+                        $bestScore = $a['score'];
+                        $best = $a;
+                    }
+                }
+                if ($best === null) {
+                    $best = $sorted[count($sorted) - 1];
+                }
+                $row = $best;
+                $row['attempts']      = count($list);
+                $row['best_score']    = $bestScore;
+                $row['attempts_list'] = $attemptsList;
+            }
+            $agg[] = $row;
+        }
+        return ['rows' => $agg, 'attempts_total' => $attemptsTotal];
+    }
 }