Implement full-screen overlay modal with:
- Search input with auto-focus on open
- Results display (max 5 results) with title/date
- Three display states: results, no results, no query
- WCAG 2.1 AA accessibility: role="dialog", aria-modal, aria-live="polite"
- Keyboard support: ESC to close, handled via handleEscape()
- Click backdrop to close, click close button
- All text localized via i18n keys
- Alpine.js 3.x integration with searchOverlay() component
