Make the history more compact and inside the app

[alainm23]

Problem

Currently, the history is displayed in an external dialog, which requires switching between two windows. In some cases, the modal becomes too large, creating visual inconsistency.

Proposal

I propose moving the history view inside the app using a Gtk.Popover or Adw.OverlaySplitView. This would allow access to the history while keeping the app in the foreground.

Prior Art (Optional)

No response

[danirabbit]

I've seen other calculators just have this directly in view above the main input and I think that makes sense. Here's a (probably old) screenshot of GNOME Calculator for example: