Delay in loading the saved theme, default light theme briefly displayed

[Gvstave]

Behaviour

When the page is loaded, the saved theme (light or dark) is not applied immediately, causing a brief flash of the light theme before transitioning to the previously selected theme. This happens even if the user had previously selected the dark theme, resulting in an inconsistent user experience.

Expected behaviour

The page should load and immediately display the previously selected theme (dark or light), without flashing the default light theme (or colouring).