Phase 7: Desktop & Wide Responsive (lg: / xl: / 2xl: / 3xl:)

[elfensky]

Progressive enhancement from tablet layout for desktop and ultrawide breakpoints.

Desktop & Wide (lg: / xl: / 2xl: / 3xl:)

• Full sidebar + map + stats layout, no vertical scrolling
• Map: hovering alert highlights related map region
• 3xl (1920px+): release max-width, go wide
• Custom ultrawide layout — use extra space meaningfully
• Test up to 21:9 ultrawide, apply max-width beyond that

Depends on: Phase 6 (Dashboard Layout), Tablet Responsive
Split from: #122

[elfensky]

Split into focused issues:

• Phase 7: Sidebar responsive scaling at xl / 2xl / 3xl breakpoints #183 — Sidebar responsive scaling at xl / 2xl / 3xl
• Phase 7: Ultrawide layout — release max-width at 3xl, cap at 21:9 #184 — Ultrawide layout at 3xl, cap at 21:9
• Phase 7: Map hover — alert highlights related map region #185 — Map hover highlights related region

Keeping this issue open as the parent tracker.