Single Source of Truth

1. Add as const to the routes object so routes.home stays the literal '/'
2. Create RouteName from the keys of routes and RoutePath from the values
3. Remove the @ts-expect-error once defaultRoute: '/' type-checks
4. Implement getRoutePath(name: RouteName): RoutePath so it returns the path for that name from routes
5. Export routes, defaultRoute, and getRoutePath by name

Completion criteria

• Named exports: routes, defaultRoute, getRoutePath
• getRoutePath('home') → '/'
• getRoutePath('login') → '/login'
• getRoutePath('settings') → '/settings'