Phase 9: Map — hovering alert highlights related map region

[elfensky]

Description

When hovering an alert card on the desktop dashboard, highlight the corresponding sector on the galaxy map. This creates a cross-panel interaction since the map is always visible alongside the sidebar.

Context

Split from #168 (Desktop & Wide Responsive). The desktop layout pins the map while the sidebar scrolls, making hover-to-highlight a natural interaction pattern.

Requirements

• Hovering an alert card highlights the related sector on the galaxy map
• Highlight should be visually distinct (e.g., pulse, glow, or opacity change)
• Desktop only (lg:+) — no effect on mobile/tablet where map and alerts aren't side-by-side
• Should not affect map performance or cause layout shifts

Key Files

• src/components/h1/Alerts/Alerts.jsx
• src/components/h1/Galaxy/Map.jsx
• src/components/h1/Dashboard/DashboardClient.jsx (state coordination)