🎨 Palette: Add accessible labels to graph tab icon buttons

[threehymns]

💡 What: Added aria-label attributes to the "Reset settings", "Close panel", and "Delete group" icon-only buttons in the Graph Controls tab. Also added a title attribute to the "Delete group" button.
🎯 Why: Icon-only buttons without accessible names are invisible to screen readers, preventing visually impaired users from understanding their purpose or interacting with them. Adding an aria-label ensures these controls are correctly announced.
📸 Before/After: Visuals are unchanged (as intended). title tooltips now display for the delete button.
♿ Accessibility: Ensures graph panel control buttons have explicitly computed accessible names.

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PR created automatically by Jules for task 4283503121399523241 started by @threehymns

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