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/comment_repo.go

@@ -2,6 +2,7 @@ package repository
 
 import (
 	"metazone.cc/metalab/internal/model"
+	"metazone.cc/metalab/internal/service"
 	"strconv"
 
 	"gorm.io/gorm"
@@ -258,6 +259,22 @@ func (r *CommentRepo) FindPostAuthorID(postID uint) (uint, error) {
 	return authorID, err
 }
 
+// AggregateCommentsByAuthor 按日期聚合评论量（作者所有文章在时间段内的评论）
+func (r *CommentRepo) AggregateCommentsByAuthor(userID uint, since string) ([]service.TrendPoint, error) {
+	var results []service.TrendPoint
+	err := r.db.Table("comments").
+		Select("TO_CHAR(comments.created_at, 'YYYY-MM-DD') AS date, COUNT(*) AS value").
+		Joins("JOIN posts ON posts.id = comments.post_id").
+		Where("posts.user_id = ? AND comments.created_at >= ?", userID, since).
+		Group("TO_CHAR(comments.created_at, 'YYYY-MM-DD')").
+		Order("date ASC").
+		Scan(&results).Error
+	if results == nil {
+		results = []service.TrendPoint{}
+	}
+	return results, err
+}
+
 // ListAllComments 后台评论列表（支持关键词搜索、分页）
 func (r *CommentRepo) ListAllComments(keyword string, showDeleted bool, offset, limit int) ([]model.AdminCommentRow, int64, error) {
 	var total int64