refactor: update styling and color classes across components

- Changed error message styling in ICalImportModal to use new color classes.
- Updated task completion styling in TaskListView to use new success color classes.
- Modified selected styling in ContactListItem tests to reflect new background class.
- Adjusted duplicate warning styling in ContactImportDialog to use new warning color classes.
- Refactored background and border colors in CalendarInvitationBanner for various statuses.
- Updated email list item and viewer components to use new warning and success color classes.
- Refined styling for unread indicators in email components.
- Enhanced error fallback styling in error components to use new warning color classes.
- Updated filter rule modal button hover styles to use new destructive color classes.
- Added experimental feature descriptions in Plugins and Themes settings.
- Refined vacation settings validation warning styling to use new warning color classes.
- Updated toast component styles to use new color classes for different states.
- Introduced a new built-in theme 'Qui' with specific color variables.
- Adjusted email security status colors to use new warning color classes.

lib/email-headers.ts

@@ -154,10 +154,10 @@ export function getSecurityStatus(result?: string): {
     case 'neutral':
     case 'temperror':
       return {
-        color: 'text-amber-700 dark:text-amber-400',
+        color: 'text-warning',
         icon: 'alert',
         bgColor: 'bg-gray-50 dark:bg-gray-800',
-        borderColor: 'border-l-4 border-amber-600 dark:border-amber-500'
+        borderColor: 'border-l-4 border-warning'
       };
     default:
       return {