🎨 Palette: Improve keyboard accessibility and focus states

[n24q02m]

💡 What: Added explicit keyboard focus capabilities to the scrollable table container (tabindex="0", role="region", aria-label) and explicit :focus-visible outline styles with an offset for navigation links, buttons, and the scroller itself to replace subtle brightness adjustments.

🎯 Why: To allow keyboard users to easily locate focused interactive elements and navigate/scroll overflow content without requiring a mouse, conforming to standard accessibility expectations.

📸 Before/After: Before, keyboard focus was either non-existent or hard to see. After, navigation and the table container show a clear explicit outline when focused with the keyboard.

♿ Accessibility: Specifically addresses WCAG guidelines for keyboard accessibility (SC 2.1.1 Keyboard) and Non-text Contrast for focus indicators (SC 1.4.11).

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PR created automatically by Jules for task 12944386854574509225 started by @n24q02m

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