feat: 编辑器增加「重置」和「丢弃预览版」按钮，支持回退预览版快照

par-core/src/main/java/com/par/core/mapper/SiteSnapshotMapper.java

@@ -23,4 +23,8 @@ public interface SiteSnapshotMapper extends BaseMapper<SiteSnapshot> {
     /** 查询站点最新快照：draft 优先，无 draft 则取 published */
     @Select("SELECT * FROM site_snapshots WHERE site_id = #{siteId} AND status IN ('draft','published') ORDER BY CASE WHEN status = 'draft' THEN 0 ELSE 1 END, version DESC LIMIT 1")
     SiteSnapshot selectLatestWithDraft(@Param("siteId") String siteId);
+
+    /** 删除站点指定状态的快照 */
+    @org.apache.ibatis.annotations.Delete("DELETE FROM site_snapshots WHERE site_id = #{siteId} AND status = #{status}")
+    int deleteBySiteIdAndStatus(@Param("siteId") String siteId, @Param("status") String status);
 }

par-core/src/main/java/com/par/core/service/SiteSnapshotService.java

@@ -71,4 +71,10 @@ public interface SiteSnapshotService {
      * @return 成功发布的站点数
      */
     int publishChanged();
+
+    /**
+     * 丢弃预览版快照（删除所有 draft 记录），回退到正式版
+     * @return 删除的 draft 记录数
+     */
+    int discardDraft(String siteId);
 }

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

@@ -333,6 +333,19 @@ public class SiteSnapshotServiceImpl implements SiteSnapshotService {
         return count;
     }
 
+    @Override
+    @Transactional
+    public int discardDraft(String siteId) {
+        int deleted = snapshotMapper.deleteBySiteIdAndStatus(siteId, "draft");
+        if (deleted > 0) {
+            jsonCache.invalidate(draftKey(siteId));
+            log.info("预览版已丢弃: siteId={}, 删除 {} 条记录", siteId, deleted);
+        } else {
+            log.info("站点 {} 无预览版可丢弃", siteId);
+        }
+        return deleted;
+    }
+
     /** 将快照转为 mediabot 可用的 JSON 字符串 */
     private String toBundleJson(SiteSnapshot snapshot) {
         try {