🎨 Palette: Add ARIA labels to icon-only buttons in message queue

[thirdeyenation]

💡 What: Added aria-label attributes to the four icon-only buttons (Send all, Clear all, Send now, Remove) in the message-queue.html component. Also added aria-hidden="true" to their inner material symbol icons.

🎯 Why: To improve keyboard and screen reader accessibility by providing descriptive labels for buttons that previously only had hover title attributes, ensuring users utilizing assistive technologies can understand the button actions. The aria-hidden="true" prevents screen readers from reading the raw material icon text (e.g., "keyboard_double_arrow_right").

📸 Before/After: Visuals remain identical (icons unchanged). Accessibility tree now properly exposes button labels.

♿ Accessibility: Improved screen reader support by providing explicit accessible names to interactive elements without visible text, aligning with WCAG guidelines for non-text content and button labeling.

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PR created automatically by Jules for task 17095267189638809156 started by @thirdeyenation

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