Hi Frank,
Your app runs (usually) in a browser. So angular is no exception for any other, you can view the source of your app.
However, Angular 2 will have a way to run it on your server, and only server the resulting HTML. That way you ca keep some/most off your app on the server. (You still need some JS on the client, no way around that)
However, this has very little to do with code security. Using angular makes your code more secure as it would be without it. For an 'attacker it's a whole lot more complex to tamper with your application.
But you have to realize, that if your expose your application to the web(this is even true for non-web apps!) security is at stake, and it is something you only can battle at your server.
Regards
Sander