Add standard keyboard scrolling to member list

[1-navneet]

Summary

Adds standard keyboard scrolling behavior to the member list so arrow and page navigation keys scroll the list instead of moving the map.

Changes

• Enable keyboard focus on member list
• Handle ArrowUp / ArrowDown / PageUp / PageDown / Home / End
• Prevent map movement while list is focused
• Add visible focus outline for accessibility

Before

• Arrow and page keys moved the map instead of scrolling the relations list.

After

• Relations list captures keyboard focus and scrolls independently without moving the map.

Notes

Improves keyboard accessibility and aligns the member list with standard sidebar scrolling behavior.