restructuring crawler architecture

src/internal/model/article.go

@@ -16,6 +16,18 @@ type Article struct {
 	AiSummary   string
 }
 
+func (a *Article) Clone() *Article {
+	return &Article{
+		Id:          a.Id,
+		SourceUrl:   a.SourceUrl,
+		PublishDate: a.PublishDate,
+		FetchDate:   a.FetchDate,
+		Title:       a.Title,
+		Content:     a.Content,
+		AiSummary:   a.AiSummary,
+	}
+}
+
 // TODO docstring
 type ArticleViewModel struct {
 	Id           int