One 'display' image resolves what it shows from its own IP, like the existing
visitor-location BU mapping. Extend DashboardDefault with displayrole
(dashboard|lobby|partskiosk; migration 7d28, businessunitid now nullable since
only the dashboard role needs one) + a role->path map. New unauthenticated
GET /api/dashboarddefaults/display-role returns {role, path, businessunitid}
for the caller IP. Settings UI gains a Display selector, showing the business
unit only for the dashboard role.
60e2947fc7