Switch ember-cli-page-object to native DOM helpers

# Problem

ember-cli-page-object now has the option to no longer rely on global test helpers and instead use native DOM helpers.

https://github.com/san650/ember-cli-page-object/releases/tag/v1.13.0

However, enabling this option in our case breaks some tests, so we need to resolve those issues.

## Subtasks
- [ ] Enable the option to use native dom helpers.
- [ ] Fix broken tests

首先查看 issue 中連結的 ember-cli-page-object v1.13.0 發行說明，並在專案設定中啟用 native DOM helpers 選項。執行測試套件以識別失敗的測試，解決這些失敗，然後確認在啟用該選項的情況下完整測試套件通過。

由索引模型根據 Issue 內容生成。