🎨 Palette: Add ARIA labels and hide text-based icons

[ralksta]

💡 What: Added aria-label and aria-hidden="true" to text-based close ('×') buttons in PageBuilder.tsx, AssetPicker.tsx, and AlbumPicker.tsx.
🎯 Why: Text characters used as visual icons (like '×') are often announced poorly by screen readers (e.g. "times" or "multiply"). By wrapping the visual character in an aria-hidden span and providing an explicit aria-label on the parent <button>, the intended action ("Clear search" or "Close modal") is communicated accurately.
📸 Before/After: Visuals remain unchanged. Screen reader output changes from reading confusing math symbols to explicit functional actions.
♿ Accessibility: Improved screen reader announcements for text-based icon buttons, providing clear actionable context instead of raw symbol names.

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PR created automatically by Jules for task 15682275450310377440 started by @ralksta

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