feat: 用户徽章与等级体系，积分经济管理重构

- 新增徽章系统：badge 服务与 handler、管理端配置页、BadgeChip/LevelBadge 展示组件
- 新增等级模型：model/level 及前端 levels 元数据
- 管理端经济模块拆分为 points/badges/levels 独立页面，EconomySettings 迁入设置
- 积分、签到、评论等服务适配等级与徽章逻辑

backend/service/post_interact.go

@@ -723,7 +723,7 @@ func (s *PostService) loadAcceptedAnswer(postID, commentID uint, floor int, view
 		return nil
 	}
 	var c model.Comment
-	err := s.db.Unscoped().Preload("User").
+	err := s.db.Unscoped().Preload("User").Preload("User.Badges.Badge").
 		Where("id = ? AND post_id = ?", commentID, postID).
 		First(&c).Error
 	if err != nil {
@@ -1039,7 +1039,7 @@ func (s *PostService) buildLotteryState(post *model.Post, viewerID uint, canMana
 // VotePoll 投票
 func (s *PostService) VotePoll(userID, postID uint, optionIndexes []int) (*PostDetail, error) {
 	var post model.Post
-	if err := s.db.Preload("Board").Preload("User").First(&post, postID).Error; err != nil {
+	if err := s.db.Preload("Board").Preload("User").Preload("User.Badges.Badge").First(&post, postID).Error; err != nil {
 		return nil, ErrPostNotFound
 	}
 	if model.NormalizePostType(post.PostType) != model.PostTypePoll {
@@ -1286,7 +1286,7 @@ func (s *PostService) AcceptBounty(actor *Actor, userID, postID, commentID uint)
 	if err != nil {
 		return nil, err
 	}
-	s.db.Preload("Board").Preload("User").First(post, post.ID)
+	s.db.Preload("Board").Preload("User").Preload("User.Badges.Badge").First(post, post.ID)
 	return s.detailAfterInteract(post, userID)
 }
 
@@ -1498,7 +1498,7 @@ func StartTypedPostSettler(s *PostService) {
 
 func (s *PostService) loadManageablePost(actor *Actor, userID, postID uint) (*model.Post, error) {
 	var post model.Post
-	if err := s.db.Preload("Board").Preload("User").First(&post, postID).Error; err != nil {
+	if err := s.db.Preload("Board").Preload("User").Preload("User.Badges.Badge").First(&post, postID).Error; err != nil {
 		return nil, ErrPostNotFound
 	}
 	if post.UserID != userID && (actor == nil || !actor.CanModerateBoard(post.BoardID)) {