Put URL into a separate field and make it clickable in GUI

Currently, the GUI often contains (non-clickable) URLs for packages. These URLs are not interesting.

**Describe the feature you want**
I want to be able to click the URLs.

For GUI design it might be nicer to have the URLs in separate fields in the JSON file.

Related, but not identical: #12

查看顯示套件資訊的 GUI 程式碼，可能在 egui 或 iced 這類 UI 函式庫中。確定當前 URL 以純文字形式渲染的位置。將 URL 分離到資料模型（JSON 結構）中的獨立欄位。更新 UI，將 URL 渲染為可點擊的超連結。透過執行 GUI 並驗證連結是否有效來測試變更。

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