🎨 Palette: Add ARIA labels to message queue buttons

[thirdeyenation]

💡 What: Added aria-label attributes to the "Send all", "Clear all", "Send now", and "Remove" icon-only buttons in the message queue component. Also added aria-hidden="true" to their inner material-symbols-outlined spans.
🎯 Why: Improves accessibility for screen reader users by providing descriptive text for icon-only action buttons and preventing the raw ligature text (e.g., "keyboard double arrow right") from being announced.
📸 Before/After: Visual appearance remains unchanged.
♿ Accessibility:

• Descriptive aria-labels provide context for screen readers.
• aria-hidden="true" on inner spans hides meaningless ligature text from assistive technologies.

---

PR created automatically by Jules for task 17626918497651805065 started by @thirdeyenation

[google-labs-jules]

👋 Jules, reporting for duty! I'm here to lend a hand with this pull request.

When you start a review, I'll add a 👀 emoji to each comment to let you know I've read it. I'll focus on feedback directed at me and will do my best to stay out of conversations between you and other bots or reviewers to keep the noise down.

I'll push a commit with your requested changes shortly after. Please note there might be a delay between these steps, but rest assured I'm on the job!

For more direct control, you can switch me to Reactive Mode. When this mode is on, I will only act on comments where you specifically mention me with @jules. You can find this option in the Pull Request section of your global Jules UI settings. You can always switch back!

New to Jules? Learn more at jules.google/docs.

---

For security, I will only act on instructions from the user who triggered this task.