🎨 Palette: Improve accessibility for text-based close buttons

[ralksta]

💡 What: Wrapped text-based icon characters ('×') in <span aria-hidden="true"> and added descriptive aria-label attributes to their parent <button> elements across picker modals and search fields.
🎯 Why: Screen readers often pronounce text characters used as icons unhelpfully (e.g. "times"). Hiding the character and providing a clear aria-label ("Close" or "Clear search") improves context and accessibility for keyboard and screen reader users.
📸 Before/After: Visuals remain unchanged, but screen reader announcements are corrected.
♿ Accessibility: Replaced poorly announced "×" characters with clear text labels ("Close" and "Clear search") via ARIA attributes.

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PR created automatically by Jules for task 14591650131220881107 started by @ralksta

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