fix: clean up unused icons and add LoadImage lucide icon override (#9359)

## Summary

Remove 46 unused snake_case SVG icons from design-system and use lucide
icon for LoadImage.

## Changes

- **What**: Remove unreferenced snake_case SVG files, replace LoadImage
custom icon with `lucide--image-up`, add `preview-image.svg` (renamed
from `image-preview.svg` to match `kebabCase('PreviewImage')`), extract
`ESSENTIALS_ICON_OVERRIDES` to `essentialsNodes.ts`
- Remove `load-image` from safelist in `style.css`

<img width="307" height="701" alt="image"
src="https://github.com/user-attachments/assets/de5e1bde-03eb-415e-ac76-f2e653a5eeb2"
/>

┆Issue is synchronized with this [Notion
page](https://www.notion.so/PR-9359-fix-clean-up-unused-icons-and-add-LoadImage-lucide-icon-override-3186d73d36508159be05ce6f4145be56)
by [Unito](https://www.unito.io)

pnpm-workspace.yaml

@@ -9,6 +9,7 @@ catalog:
   '@iconify-json/lucide': ^1.1.178
   '@iconify/json': ^2.2.380
   '@iconify/tailwind4': ^1.2.0
+  '@iconify/utils': ^3.1.0
   '@intlify/eslint-plugin-vue-i18n': ^4.1.1
   '@lobehub/i18n-cli': ^1.26.1
   '@nx/eslint': 22.5.2