Fix dark mode readability and input elements using light theme

[Hezer]

Found couple issues/improvements with the dark mode, where it wasn't applied or the elements had low visibility.
This should fix the following:

• Low readability with Danger, Warning, and Success colored elements. (buttons & labels)
• Low visibility of the closing "X" button on dialog modals
• Checkboxes were still using light theme. Added property color-scheme: dark to correct it with input elements when dark mode is active

[ShreyasZare]

Thanks for the PR. Will review it soon.