VSN-2759/ feat: representative login flow, passenger selection, and representative-aware data access

This MR includes the following changes :

• Representative auth flow: after login, if userType is REPRESENTATIVE, the user is redirected to a passenger selection screen. Once a passenger is selected, they access that passenger's space. On app restart, the selected passenger is restored from AsyncStorage.
  • Passenger selection screen: lists all linked passengers with avatar, name, and navigation arrow. Auto-selects if only one passenger is linked.
  • Representative-aware data access: added resolvePassengerUuid() utility that returns selectedPassengerUuid for representatives and userUuid for passengers. Applied to all stores: planning, timetable, tracking, absence, documents, and schedule config.
  • Personalized greeting: home screen shows the representative's first name (matched from the passenger's representatives list) or the passenger's first name depending on the logged-in account