🎨 Palette: Make ClassificationPreview actions accessible

[thebearwithabite]

💡 What: Added aria-labels, aria-hidden attributes, and focus-visible keyboard navigation styles to the action buttons in ClassificationPreview.
🎯 Why: Keyboard users couldn't navigate or easily see focus states on the organize/reclassify/skip actions, and screen readers read redundant icon text.
📸 Before/After: N/A
♿ Accessibility: Added explicit focus rings for keyboard navigation, hid decorative Lucide icons from screen readers, and labeled icon-only buttons.

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PR created automatically by Jules for task 15596388641130109506 started by @thebearwithabite

[google-labs-jules]

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