Style: Design System use across more components (#6705)

## Summary

Only remaining use is in `buttonTypes.ts` which @viva-jinyi is going to
be working on to consolidate our different buttons soon.

## Changes

- **What**: Replace light/dark colors with theme aware design system
tokens.

## Review Focus

Double check the chosen colors for the components

## Screenshots

| Before | After |
| ------ | ----- |
| <img width="607" height="432" alt="image"
src="https://github.com/user-attachments/assets/6c0ee6d6-819f-40b1-b775-f8b25dd18104"
/> | <img width="646" height="488" alt="image"
src="https://github.com/user-attachments/assets/9c8532de-8ac6-4b48-9021-3fd0b3e0bc63"
/> |

┆Issue is synchronized with this [Notion
page](https://www.notion.so/PR-6705-Style-WIP-Design-System-use-across-more-components-2ab6d73d365081619115fc5f87a46341)
by [Unito](https://www.unito.io)

---------

Co-authored-by: github-actions <github-actions@github.com>

src/components/widget/layout/BaseModalLayout.vue

@@ -132,8 +132,7 @@ const toggleRightPanel = () => {
 // Computed classes for better readability
 const layoutClasses = cn(
   'base-widget-layout',
-  'rounded-2xl overflow-hidden relative',
-  'bg-gray-50 dark-theme:bg-smoke-800'
+  'rounded-2xl overflow-hidden relative'
 )
 
 const rightPanelButtonClasses = computed(() => {
@@ -148,10 +147,7 @@ const closeButtonClasses = cn(
   'transition-opacity duration-200'
 )
 
-const mainContainerClasses = cn(
-  'flex-1 flex',
-  'bg-smoke-100 dark-theme:bg-neutral-900'
-)
+const mainContainerClasses = cn('flex-1 flex bg-base-background')
 
 const headerClasses = cn(
   'w-full h-18 px-6',