To make a login form on every page, just either include the login view as well, or copy that form. Tank Auth is dependent on the name of the fields - so just make sure there are no collisions. I alter this once to have login and registration on the same page, and noticed there that they look at the same field names. Had to edit some of the library to fix that.
edit: if you want them to stay on the page, or return to the page they were on after logging in, you would need to do a bit more work. I think if I remember right, that it has them go to index.php after logging in.