🎨 Palette: Add ARIA labels to message queue buttons

[thirdeyenation]

💡 What
Added aria-label attributes to the icon-only buttons in the message queue component (Send all, Clear all, Send now, Remove) and added aria-hidden="true" to their internal icon spans.

🎯 Why
Icon-only buttons without accessible labels are invisible to screen readers, leaving users reliant on assistive technology unable to understand what these buttons do. The aria-hidden="true" prevents screen readers from redundantly reading the raw ligature text (like "keyboard_double_arrow_right").

📸 Before/After
(No visual changes, purely markup and accessibility improvements)

♿ Accessibility

• Improved screen reader support for the message queue interface by providing clear, descriptive labels matching the existing tooltips.
• Prevented ligature text from being misread.

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PR created automatically by Jules for task 5460614130826965540 started by @thirdeyenation

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