Introduce gamification and check-in support plus expanded transport/admin APIs. Added DDL for checkins, badges and user_badges. New repositories: badgeRepository, userBadgeRepository, checkinRepository. New routes: admin badge management, admin transport (lines/platforms/stations), public transport endpoints, user checkins and stations endpoints, and user badges on /me. Services updated: adminService (badge CRUD & user assignment), userService (checkins, badge queries), authService (hasAdminRights). Minor package.json name update. These changes implement database, repo, service and route wiring for badges, user_badins and checkin features and additional transport admin routes.
