task-56: 采集结果 Excel 改为临时文件+原子落位，流式写入或落位失败时清理临时文件，目标路径不残留半成品

backend-java/src/main/java/com/nanri/aiimage/modules/collectdata/service/CollectDataExcelAssemblyService.java

@@ -11,6 +11,9 @@ import org.springframework.stereotype.Service;
 
 import java.io.File;
 import java.io.FileOutputStream;
+import java.io.IOException;
+import java.nio.file.Files;
+import java.nio.file.StandardCopyOption;
 import java.util.LinkedHashMap;
 import java.util.List;
 import java.util.Locale;
@@ -51,14 +54,25 @@ public class CollectDataExcelAssemblyService {
                                        List<CollectDataResultRowVo> items,
                                        List<CollectDataSummaryRowDto> summaries,
                                        Supplier<List<CollectDataResultRowVo>> rawItemsSupplier) {
+        if (outputXlsx == null) {
+            throw new BusinessException("生成采集数据 Excel 失败: 输出文件路径为空");
+        }
         SXSSFWorkbook workbook = new SXSSFWorkbook(200);
         workbook.setCompressTempFiles(true);
-        try (FileOutputStream outputStream = new FileOutputStream(outputXlsx)) {
+        // 先写目标同目录的临时文件，成功后原子落位：写入或落位失败时目标路径
+        // 不残留半成品，临时文件由 catch/finally 清理（SXSSF 滚动窗口文件由 dispose 释放）。
+        File tmpFile = new File(outputXlsx.getAbsolutePath() + ".tmp");
+        try {
             writeDetailSheet(workbook, items);
             writeSummarySheet(workbook, summaries, rawItemsSupplier);
-            workbook.write(outputStream);
+            try (FileOutputStream outputStream = new FileOutputStream(tmpFile)) {
+                workbook.write(outputStream);
+            }
+            Files.move(tmpFile.toPath(), outputXlsx.toPath(),
+                    StandardCopyOption.REPLACE_EXISTING, StandardCopyOption.ATOMIC_MOVE);
         } catch (Exception ex) {
             log.warn("[collect-data] write workbook failed: {}", ex.getMessage());
+            deleteQuietly(tmpFile);
             throw new BusinessException("生成采集数据 Excel 失败: " + ex.getMessage());
         } finally {
             try {
@@ -66,6 +80,15 @@ public class CollectDataExcelAssemblyService {
             } catch (Exception ignored) {
             }
             workbook.dispose();
+            deleteQuietly(tmpFile);
+        }
+    }
+
+    private void deleteQuietly(File file) {
+        try {
+            Files.deleteIfExists(file.toPath());
+        } catch (IOException ex) {
+            log.warn("[collect-data] delete workbook temp file failed: {}", ex.getMessage());
         }
     }