🎨 Palette: Enhance accessibility for anchor tag buttons

[0m364]

🎨 Palette: Enhance accessibility for anchor tag buttons

💡 What: Added role="button" and aria-haspopup="dialog" to the #sitrep-btn anchor tags in concepts.html, products.html, and contact.html. Added a keydown event listener in modal.js to trigger the modal using the Spacebar while preventing page scroll.
🎯 Why: Native <a> tags used as buttons do not communicate their behavior to screen readers and only respond to the Enter key. Keyboard users expect buttons to respond to Spacebar as well. This makes the OSINT modal button fully accessible.
📸 Before/After: Button works exactly the same visually, but responds to Spacebar and announces correctly to screen readers.
♿ Accessibility: Improves semantics and keyboard interaction parity for users relying on assistive technology.

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PR created automatically by Jules for task 5857668996377132617 started by @0m364

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