🎨 Palette: Add button role and spacebar support to modal triggers

[0m364]

💡 What: Added role="button", aria-haspopup="dialog", and spacebar key support to the #sitrep-btn modal triggers across all pages.
🎯 Why: Native <a> tags with href="#" only trigger on the Enter key. Keyboard and screen reader users expect elements acting as buttons to also trigger on the Spacebar key and to have the semantic role="button".
📸 Before/After: Visuals remain unchanged, but keyboard interaction now works as expected without scrolling the page down.
♿ Accessibility: Ensures WCAG compliance for interactive element roles and keyboard support for modal triggers.

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PR created automatically by Jules for task 15110168249223573647 started by @0m364

[google-labs-jules]

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