Security risk! -> hide saved password for SMB access

[user4andre]

I use the app on a tablet. As the tablet is also to be used by guests who have read access to the data provided via SMB, I want to hide the password for SMB access.

As displaying the password can be helpful when setting up a connection, there should be a button to hide it permanently from this point on.

In this context, #1302 should also be resolved.