galaxy(ui): mini-map and Helm integration

[ScottyVenable]

Owner: Sol
Parent: #91

Goal

Promote the galaxy map from feature-flag scaffold to the canonical Helm
experience and slot the MiniMap into the desktop right rail.

Acceptance criteria

• flags.galaxyMap removed (or defaulted true) once sub-tasks 1 and 2
  land; the Helm screen renders GalaxyMap + SystemMap directly.
• MiniMap rendered inside RightRail on viewports >= 960px.
• Clicking a system in the mini-map pans / centres the main galaxy map
  on that system.
• The text-list "Destinations" card stays as a secondary navigation aid;
  selecting a system on the map syncs the destination list selection
  and vice-versa.
• Course plotting (Engage Drive, fuel cost, days, events) continues to
  work without regression on both layouts.
• Reduced-motion preference respected for the map → list sync animation.

Out of scope

Pan/zoom gesture refinement (sub-task 1) and station marker styling
(sub-task 2).

Branch suggestion

feat/sol-helm-map-integration