🎨 Palette: Improve accessibility of collapsible UI components

[d3mocide]

🎨 Palette: Improve accessibility of collapsible UI components

💡 What:

• Added aria-expanded and aria-controls to the toggle button in the CollapsibleSection component (used heavily in the JS8Call ListeningPost).
• Used React's useId() hook to dynamically generate a unique ID for the content block to properly associate with aria-controls.
• Added missing keyboard focus states (focus-visible:ring-1 focus-visible:ring-cyan-500 outline-none) to the toggle button.
• Added aria-hidden="true" to purely decorative SVG icons within the button.
• Applied identical accessibility improvements to the "Manual Entry" toggle block in KiwiNodeBrowser.tsx (hardcoded ID since it is a single instance).

🎯 Why:
Screen reader users navigating custom accordion or collapsible blocks were previously unaware of the section's expanded/collapsed state or which content it controlled because the buttons lacked the semantic ARIA hooks (aria-expanded and aria-controls). Additionally, keyboard-only users lacked a clear visual indicator of which section was currently focused.

♿ Accessibility:

• Explicitly binds the toggle button to its content container via aria-controls.
• Exposes state via aria-expanded.
• Restores keyboard focus visibility.
• Hides decorative Chevrons from screen readers to reduce noise.

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PR created automatically by Jules for task 14437336375247061650 started by @d3mocide

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