feat: 类型帖互动、积分经济与发帖体验

补齐问答采纳/重开、投票匿名与有票禁编、悬赏过期退回、抽奖回帖开奖，并接入积分账本与发帖附件可见性。

Co-authored-by: Cursor <cursoragent@cursor.com>

backend/service/moderation.go

@@ -171,7 +171,14 @@ func (s *ModerationService) ApprovePost(actor *Actor, id uint) (boardID uint, er
 		if post.Status != model.ContentStatusPending {
 			return ErrNotPending
 		}
-		if err := tx.Model(&post).Update("status", model.ContentStatusPublished).Error; err != nil {
+		updates := map[string]interface{}{
+			"status": model.ContentStatusPublished,
+		}
+		// 悬赏/抽奖：首次公开发布时补写 ends_at
+		if raw, ok := EnsureDeadlineOnPublish(post.TypeMeta, post.PostType, time.Now().UTC()); ok {
+			updates["type_meta"] = raw
+		}
+		if err := tx.Model(&post).Updates(updates).Error; err != nil {
 			return err
 		}
 		boardID = post.BoardID