Are stellar spectra unique enough that they could be used to identify particular stars? If so, has any attempt been made to use them for navigation or equipment alignment?
No, you can't use them to identify your star. Indeed, you have too many stars in the universe. Even in our galaxy you can find two stars which have pretty much the same spectrum. You can classify the star though.
There is another problem with redshift and blueshift. It change the spectrum of the star depending its movement.