Fix tag entry UI.

[TurboGit]

1. Make the dialog a bit larger
2. Rework color to ensure the selection is seen

Closes #19896
Closes #20051

[TurboGit]

@zisoft : If you have an X11 box (I'm currently only with Wayland), can you check this? TIA.

[zisoft]

No X11, I am on a Mac.

Unfortunately not fixed, still no highlight when using the arrow keys:

Highlight on mouse hover works fine.

[zisoft]

very strange, when I set

#tag-completion *:selected
{
  background-color: green;
}

it works:

[zisoft]

@TurboGit:

the color should be @selected_bg_color

[TurboGit]

@zisoft : You're using which theme?

[TurboGit]

Tested with @selected_bg_color on darker, dark and grey theme. All ok on my side on Wayland.

[zisoft]

@TurboGit : I use darktable-elegant-grey

[TurboGit]

@TurboGit : I use darktable-elegant-grey

Strange that is was ok on my side as I'm using the same theme.