🎨 Palette: Improve accessibility of CollapsibleSection in ListeningPost

[d3mocide]

💡 What: Added missing ARIA attributes (aria-expanded, aria-controls) to the CollapsibleSection component in the ListeningPost and ensured focus-visible styling for keyboard navigation.
🎯 Why: To improve accessibility for screen reader users by properly conveying the expanded/collapsed state and linking the toggle to its corresponding content area. This addresses the missing ARIA labels on accordion-style toggle buttons.
♿ Accessibility:

• Added aria-expanded reflecting the isOpen state.
• Added aria-controls binding to the content div's id.
• Added standard application focus-visible rings for keyboard navigation.

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PR created automatically by Jules for task 17444722291969645452 started by @d3mocide

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