🎨 Palette: Add focus-visible offset styles to BookDetailsPanel buttons

[jspann21]

🎨 Palette: Add focus-visible offset styles to BookDetailsPanel buttons

💡 What: Added standard focus-visible:ring-offset-2, focus-visible:ring-offset-white, and dark:focus-visible:ring-offset-slate-900 classes to the shared button variables in BookDetailsPanel.tsx. Cleaned up duplicate focus classes on inline action buttons (Save, Rescan, Open, Hide, Delete, Undo).
🎯 Why: Without these offset classes, keyboard navigation focus rings lack contrast against the panel background, making it difficult for keyboard users to see which element is focused. Consolidating the focus styling in the shared constants prevents visual drift.
📸 Before/After: Verified via headless screenshot generation during task execution.
♿ Accessibility: Improves keyboard navigation visibility (WCAG Focus Visible compliance) in the book details drawer.

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PR created automatically by Jules for task 17735496807206389785 started by @jspann21

[google-labs-jules]

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