[backport core/1.30]: UI color updates & tweaks (#6679)

## Summary
Backports PR #6381 (UI color updates & tweaks) to core/1.30 branch.

This includes:
- Text readability improvements
- Semantic color token consistency updates
- UI element styling refinements
- Component import path fixes (ComfyLogoTransparent → ComfyLogo)

## Merge Conflicts Resolved
- **ComfyMenuButton.vue**: Accepted cherry-picked version with import
changes
- **20 browser test snapshots**: Used backportee's copy as instructed

**Original commit**: fd236b3587

┆Issue is synchronized with this [Notion
page](https://www.notion.so/PR-6679-Backport-PR-6381-to-core-1-30-UI-color-updates-tweaks-2aa6d73d3650815689defd191e3dd86e)
by [Unito](https://www.unito.io)

---------

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

src/components/load3d/Load3dViewerContent.vue

@@ -9,7 +9,7 @@
     <div ref="mainContentRef" class="relative flex-1">
       <div
         ref="containerRef"
-        class="comfy-load-3d-viewer absolute h-full w-full"
+        class="comfy-load-3d-viewer absolute size-full"
         @resize="viewer.handleResize"
       />
     </div>