🎨 Palette: Add ARIA labels to icon-only buttons

[Bhishaj9]

💡 What: Added aria-label attributes to icon-only buttons (like Deploy, Copy JSON, Download JSON) and added aria-hidden="true" to the Material Symbol span elements within them across dashboard.html, glassui.html, and code.html. Also created .jules/palette.md to document the learning.
🎯 Why: To improve accessibility for screen reader users, who otherwise would not be able to understand the purpose of buttons that only contain icons, or might hear the raw ligature text (like "rocket_launch") read aloud.
📸 Before/After: Visual appearance remains the same, but accessibility is greatly improved.
♿ Accessibility: Improved screen reader compatibility for interactive elements without visible text.

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PR created automatically by Jules for task 9372336539953175344 started by @Bhishaj9

[google-labs-jules]

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