Angular: support dark mode

[yvespp]

Newer bootstrap versions support dark mode out of the box: https://getbootstrap.com/docs/5.3/customize/color-modes/

Some components need to be change to make it work:

• ng-select doesn't support dark mode out of the box. Replace with ngbDropdownToggle? Add CSS?
• Pagination remains with regardless of the theme.
• Deployment in progress are shown in white
• Inputs are shown in white -> ngbDropdownToggle?
• Modal close button
• Toast graphics
• More?

A toggle in the toolbar should be added to change the theme.