Django logins are handled by a session, and sessions are saved by the Session middleware when the response is passed back to the client. Django's builtin login call returns a response that sets the new session for the logged in user; however, you're throwing away that information and returning your own response, so the session isn't being saved.
If you want to persist the session, you'll need to pull the relevant session keys over from the response returned by the login call, and attach them to the redirect response (or find some other sequence of events that will let you get to the manage view).
Yours,
Russ Magee %-)