🎨 Palette: [UX improvement] Add keyboard accessibility for scrollable tables and focus states

[n24q02m]

💡 What: Added tabindex="0", role="region", and aria-label="Measurement results" to the overflow table container. Also added a global *:focus-visible outline for keyboard navigators.
🎯 Why: Scrollable overflow containers (like data tables on narrow screens) trap content out of reach for keyboard-only users unless explicitly made focusable. Global focus styles ensure consistent visibility when tabbing through the site.
📸 Before/After: (See PR for screenshots of the new outline on buttons and the table container).
♿ Accessibility: Fixes a critical WCAG violation by allowing keyboard and screen reader users to discover and navigate clipped content. Focus rings now meet contrast standards.

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PR created automatically by Jules for task 6023895594475083525 started by @n24q02m

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