On a mobile, why is the search bar position different in an web app and a mobile app?

What is the ideal position of the search bar on the mobile screen? Is it in the top-right corner or at the bottom?
Here is an web-app.

In this case, the search bar is placed at the top.

In addition to this, why is the position of the search bar different between a mobile app and an web app?

[Edited] My question is regarding the position of the search bar in terms of accessibility and when the search is your primary feature. Should it be placed at the top or bottom like in apps?