feat: 快照API响应增加顶层version字段，与check接口保持一致

par-core/src/main/java/com/par/core/service/impl/SiteSnapshotServiceImpl.java

@@ -351,6 +351,7 @@ public class SiteSnapshotServiceImpl implements SiteSnapshotService {
         try {
             Map<String, Object> bundle = new LinkedHashMap<>();
             bundle.put("siteId", snapshot.getSiteId());
+            bundle.put("version", snapshot.getVersion());
             bundle.put("checksum", snapshot.getChecksum());
             bundle.put("generatedAt", snapshot.getPublishedAt() != null
                     ? snapshot.getPublishedAt().toString() : LocalDateTime.now().toString());