feat(复习): 节点级 focusPath + findNode，回退 session 维度

- 移除 MindMapNode.sessionNum、filterBySession、getTaskSessions
- 新增 MindMapTreeTool.extractSubtree() 按路径提取子树作为对比基准
- 新增 findClosestNode/getPath/similarityScore 支持节点匹配
- 新增 POST /review/standard-mind-map/{taskNum}/find-node
- recallCompare 使用 focusPath 替代 sessionNum
- ReviewRecallRecordEntity.focusPath 替代 sessionNum
- Flyway V20260706_1: review_recall_records 加 focus_path 列

src/main/java/com/guo/learningprogresstracker/service/impl/StudySessionsServiceImpl.java

@@ -5,7 +5,6 @@ import com.baomidou.mybatisplus.extension.plugins.pagination.Page;
 import com.baomidou.mybatisplus.extension.service.impl.ServiceImpl;
 import com.google.protobuf.ServiceException;
 import com.guo.learningprogresstracker.dto.StudySessionsDto;
-import com.guo.learningprogresstracker.dto.response.SessionBriefVO;
 import com.guo.learningprogresstracker.dto.response.StudySessionResponse;
 import com.guo.learningprogresstracker.entity.StudyReportFragmentsEntity;
 import com.guo.learningprogresstracker.entity.StudyReportsEntity;
@@ -27,7 +26,6 @@ import org.springframework.transaction.annotation.Transactional;
 
 import java.time.LocalDateTime;
 import java.util.ArrayList;
-import java.util.List;
 import java.util.Optional;
 import java.util.stream.Collectors;
 
@@ -227,34 +225,6 @@ public class StudySessionsServiceImpl extends ServiceImpl<StudySessionsMapper, S
         return result;
     }
 
-    // ============ 获取任务会话列表（复习维度选择用） ============
-
-    @Override
-    public List<SessionBriefVO> getTaskSessions(String taskNum) {
-        var sessions = this.list(Wrappers.lambdaQuery(StudySessionsEntity.class)
-                .eq(StudySessionsEntity::getTaskNum, taskNum)
-                .orderByDesc(StudySessionsEntity::getStartTime));
-
-        return sessions.stream().map(s -> {
-            SessionBriefVO vo = new SessionBriefVO();
-            vo.setSessionNum(s.getSessionNum());
-            vo.setStartTime(s.getStartTime() != null ? s.getStartTime().toString() : null);
-            // 查询该会话的预期
-            Optional.ofNullable(studyExpectationsService.getBySessionNum(s.getSessionNum()))
-                    .ifPresent(e -> vo.setExpectation(e.getDescription()));
-            // 统计报告和残片数量
-            long reportCount = studyReportsMapper.selectCount(
-                    Wrappers.lambdaQuery(StudyReportsEntity.class)
-                            .eq(StudyReportsEntity::getSessionNum, s.getSessionNum()));
-            long fragmentCount = studyReportFragmentsMapper.selectCount(
-                    Wrappers.lambdaQuery(StudyReportFragmentsEntity.class)
-                            .eq(StudyReportFragmentsEntity::getSessionNum, s.getSessionNum()));
-            vo.setReportCount((int) reportCount);
-            vo.setFragmentCount((int) fragmentCount);
-            return vo;
-        }).collect(Collectors.toList());
-    }
-
     // ============ 活跃会话查询 ============
 
     /**