#22 完了

frontend/src/App.tsx

@@ -19,7 +19,8 @@ type Post = { id:         number
               url:        string
               title:      string
               thumbnail:  string
-              tags:       Tag[] }
+              tags:       Tag[]
+              viewed:     boolean }
 
 type User = { id:               number
               name:             string | null