task-4: 解析接口只返回固定数量预览行，完整行仅保存在后端任务载荷

parseAndCreateTask 响应 items/groups 改为 buildResponsePreviewRows/Groups 裁剪
到 PARSE_RESPONSE_PREVIEW_LIMIT(100) 行：大文件(5000行)响应体不再携带全量行，
前端/队列只依赖统计字段与 taskId，Python 通过 parsed-payload 接口拉全量。
groups 预览副本保留 itemCount 与行级字段，字段完整且顺序稳定。
8 个测试覆盖 150/5000/1/100/101 行、空文件、非法输入、存储失败恢复与临时文件清理。

backend-java/src/main/java/com/nanri/aiimage/modules/similarasin/service/SimilarAsinTaskService.java

@@ -497,8 +497,8 @@ public class SimilarAsinTaskService {
         vo.setAiPrompt(normalize(request.getAiPrompt()));
         vo.setImgSwitch(Boolean.TRUE.equals(request.getImgSwitch()));
         vo.setCategorySwitch(Boolean.TRUE.equals(request.getCategorySwitch()));
-        vo.setItems(new ArrayList<>(allRows));
-        vo.setGroups(groups);
+        vo.setItems(buildResponsePreviewRows(allRows));
+        vo.setGroups(buildResponsePreviewGroups(groups));
         long finishedAt = System.nanoTime();
         log.info("[similar-asin] parse timing taskId={} files={} rows={} groups={} totalMs={} parseMs={} groupMs={} taskInsertMs={} payloadJsonMs={} payloadStoreMs={} persistMs={} responseMs={}",
                 task.getId(),
@@ -1468,6 +1468,30 @@ public class SimilarAsinTaskService {
         return groups;
     }
 
+    private List<SimilarAsinParsedGroupVo> buildResponsePreviewGroups(List<SimilarAsinParsedGroupVo> groups) {
+        if (groups == null || groups.isEmpty()) {
+            return List.of();
+        }
+        int limit = Math.min(PARSE_RESPONSE_PREVIEW_LIMIT, groups.size());
+        List<SimilarAsinParsedGroupVo> preview = new ArrayList<>(limit);
+        for (int i = 0; i < limit; i++) {
+            SimilarAsinParsedGroupVo group = groups.get(i);
+            if (group == null) {
+                continue;
+            }
+            SimilarAsinParsedGroupVo copy = new SimilarAsinParsedGroupVo();
+            copy.setSourceFileKey(group.getSourceFileKey());
+            copy.setSourceFilename(group.getSourceFilename());
+            copy.setGroupKey(group.getGroupKey());
+            copy.setBaseId(group.getBaseId());
+            copy.setDisplayId(group.getDisplayId());
+            copy.setItemCount(group.getItemCount());
+            copy.setItems(buildResponsePreviewRows(group.getItems()));
+            preview.add(copy);
+        }
+        return preview;
+    }
+
     private List<SimilarAsinParsedRowVo> buildResponsePreviewRows(List<SimilarAsinParsedRowVo> rows) {
         if (rows == null || rows.isEmpty()) {
             return List.of();