Onboarding experience for new users

The application relies on the user being fairly familiar with how 5kmrun operates. This assumption may not always be true. We can create a light onboarding experience that walks the user through the main functionalities of the application:
* The dashboard
* The barcode
* The Selfie runs
* The events page

在程式碼庫中尋找現有的 onboarding 流程或教學畫面，它們可能位於 lib/ 目錄中。Issue 提到了四個具體區域：dashboard、barcode、selfie runs 和 events page。找到對應的畫面或 widget，以了解它們目前的狀態。新貢獻者需要設計並實作一個多步驟 walkthrough，並將其整合到應用程式的導覽中。

由索引模型根據 Issue 內容生成。