🎨 Palette: Make anchor buttons accessible

[0m364]

💡 What: Added role="button" and aria-haspopup="dialog" to #sitrep-btn anchor tags and implemented Spacebar keyboard support in modal.js.
🎯 Why: When using <a> tags with href="#" as buttons, screen readers announce them as links, and native anchors do not respond to the Space key like standard buttons do. This causes accessibility issues for keyboard and screen reader users.
📸 Before/After: N/A (Non-visual interaction change).
♿ Accessibility: Improves semantic meaning and adds required keyboard interaction (Spacebar to activate without scrolling) to emulated buttons, ensuring WCAG compliance for interactive elements.

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PR created automatically by Jules for task 5803390898123867131 started by @0m364

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