🎨 Palette: Add ARIA labels to icon-only buttons

[threehymns]

💡 What: Added aria-label attributes to multiple icon-only buttons in GraphTab and CodeBlockCodemirror.
🎯 Why: To improve screen reader accessibility for buttons that visually convey meaning through icons but lack semantic text content.
♿ Accessibility: Ensures that screen reader users hear a descriptive label (e.g., "Language Select", "Delete group") when navigating through interactive elements, rather than just "button".

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PR created automatically by Jules for task 9065910241142690281 started by @threehymns

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