Fix Gallery preview overlay and backdrop

[MMP0]

Fixes: #5971

• Restore Gallery translucent background lost during migration from Tailwind CSS (d6fbc32)
  

  gradio/ui/packages/app/src/components/Gallery/Gallery.svelte

  Line 124 in 43f5cf5

  class="absolute group inset-0 z-10 flex flex-col bg-white/90 dark:bg-gray-900 backdrop-blur h-full"

  gradio/ui/packages/gallery/src/Gallery.svelte

  Lines 184 to 185 in d6fbc32

  	backdrop-filter: blur(8px);
  	background: var(--color-background-primary);

  Before	After

• Fix Gallery preview overlay not filling width in Firefox

  Before	After

• Fix overflowing Gallery preview overlay

  Before	After

[gradio-pr-bot]

🪼 branch checks and previews

•	Name	Status	URL
	Spaces	ready!	Spaces preview
	Website	building...
	Storybook	ready!	Storybook preview
🦄	Changes	detected!	Details

---

Install Gradio from this PR

pip install https://gradio-builds.s3.amazonaws.com/c82cd0164dc484750422e5117dbb46e249851720/gradio-4.19.1-py3-none-any.whl

Install Gradio Python Client from this PR

pip install "gradio-client @ git+https://github.com/gradio-app/gradio@c82cd0164dc484750422e5117dbb46e249851720#subdirectory=client/python"

[gradio-pr-bot]

🦄 change detected

This Pull Request includes changes to the following packages.

Package	Version
@gradio/app	patch
@gradio/gallery	patch
gradio	patch

• Maintainers can select this checkbox to manually select packages to update.

With the following changelog entry.

Fix Gallery preview overlay and backdrop

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[dawoodkhan82]

Tested and fixes the issues. Thanks @MMP0!