🎨 Palette: Make anchor-based modal buttons accessible to keyboard users

[0m364]

💡 What: Added role="button" and aria-haspopup="dialog" to the #sitrep-btn anchor tags across HTML files, and implemented a keydown listener in modal.js to trigger the modal via the Spacebar.
🎯 Why: To ensure semantic correctness and provide keyboard functionality parity. Anchor tags natively only trigger on the Enter key, while screen reader and keyboard users expect interactive 'buttons' to respond to the Spacebar as well.
📸 Before/After: No visual change.
♿ Accessibility: Users navigating via keyboard can now predictably activate the "OSINT" modal using the Spacebar, and screen readers will correctly announce the element as a button rather than a link.

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PR created automatically by Jules for task 5315420440353117592 started by @0m364

[google-labs-jules]

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