feat: 收藏夹系统 + Studio 趋势图 + 通知偏好设置

- 新增收藏夹系统 (Folder/FolderItem 模型、CRUD API、前端管理页)
- 新增文章详情页收藏按钮 (书签图标、ToggleFavorite 一键收藏)
- 新增 Studio 趋势图 (赋能值/评论/点赞/收藏 4 线图, 7d/30d/90d)
- 新增通知偏好设置页 (评论/回复/点赞/关注 4 类开关)
- 后端通知列表支持按偏好过滤 (排除已关闭的通知类型)
- 下载 Chart.js 到本地静态资源 (static/js/chart.umd.min.js)
- 补充收藏夹卡片、开关滑块、趋势图网格等 CSS 样式

internal/repository/energy_repo.go

@@ -146,3 +146,19 @@ func (r *EnergyRepo) ListAllEnergyLogs(energyType string, offset, limit int) ([]
 	err := query.Order("created_at DESC").Offset(offset).Limit(limit).Find(&logs).Error
 	return logs, total, err
 }
+
+// AggregateEnergyByAuthor 按日期聚合赋能值（作者所有文章在时间段内的赋能记录）
+func (r *EnergyRepo) AggregateEnergyByAuthor(userID uint, since string) ([]service.TrendPoint, error) {
+	var results []service.TrendPoint
+	err := r.db.Table("post_energize_logs").
+		Select("TO_CHAR(post_energize_logs.created_at, 'YYYY-MM-DD') AS date, COALESCE(SUM(post_energize_logs.amount), 0) AS value").
+		Joins("JOIN posts ON posts.id = post_energize_logs.post_id").
+		Where("posts.user_id = ? AND post_energize_logs.created_at >= ?", userID, since).
+		Group("TO_CHAR(post_energize_logs.created_at, 'YYYY-MM-DD')").
+		Order("date ASC").
+		Scan(&results).Error
+	if results == nil {
+		results = []service.TrendPoint{}
+	}
+	return results, err
+}