[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/controls/SceneControls.vue

@@ -24,7 +24,7 @@
           ref="colorPickerRef"
           type="color"
           :value="backgroundColor"
-          class="pointer-events-none absolute m-0 h-0 w-0 p-0 opacity-0"
+          class="pointer-events-none absolute m-0 size-0 p-0 opacity-0"
           @input="
             updateBackgroundColor(($event.target as HTMLInputElement).value)
           "
@@ -45,7 +45,7 @@
           ref="imagePickerRef"
           type="file"
           accept="image/*"
-          class="pointer-events-none absolute m-0 h-0 w-0 p-0 opacity-0"
+          class="pointer-events-none absolute m-0 size-0 p-0 opacity-0"
           @change="uploadBackgroundImage"
         />
       </Button>