feat(复习): 支持会话维度复习 + 标准导图按会话过滤（后端）

- MindMapNode 新增 sessionNum 字段
- BuiltinMindMapGenerator 生成节点时填充 sessionNum
- MindMapTreeTool.filterBySession() 按会话过滤标准导图
- recallCompare 接受 sessionNum 参数
- ReviewRecallRecordEntity 新增 sessionNum 字段
- Flyway V20260705_1: review_recall_records 加 session_num 列
- 新增 GET /study-sessions/tasks/{taskNum}/sessions 端点

src/main/java/com/guo/learningprogresstracker/controller/ReviewController.java

@@ -154,7 +154,7 @@ public class ReviewController {
     public CommonResult<ReviewStandardMindMapEntity> recallCompare(
             @PathVariable String taskNum,
             @Valid @RequestBody RecallCompareRequest request) throws NotFindEntitiesException, OperationFailedException {
-        return CommonResult.success(standardMindMapService.recallCompare(taskNum, request.getRecallOutline()));
+        return CommonResult.success(standardMindMapService.recallCompare(taskNum, request.getRecallOutline(), request.getSessionNum()));
     }
 
     /**

src/main/java/com/guo/learningprogresstracker/controller/StudySessionController.java

@@ -18,7 +18,9 @@ import lombok.RequiredArgsConstructor;
 import org.springframework.validation.annotation.Validated;
 import org.springframework.web.bind.annotation.*;
 
+import com.guo.learningprogresstracker.dto.response.SessionBriefVO;
 import java.util.ArrayList;
+import java.util.List;
 import java.time.LocalDateTime;
 
 /**
@@ -137,4 +139,10 @@ public class StudySessionController {
             @RequestParam(required = false) String excludeTaskNum) {
         return CommonResult.success(studySessionsServiceImpl.getActiveSession(excludeTaskNum));
     }
+
+    /** 获取任务的所有会话简要列表（用于复习维度选择） */
+    @GetMapping("/tasks/{taskNum}/sessions")
+    public CommonResult<List<SessionBriefVO>> getTaskSessions(@PathVariable String taskNum) {
+        return CommonResult.success(studySessionsServiceImpl.getTaskSessions(taskNum));
+    }
 }