Same profile can be added multiple times

[shuuji3]

Problem

The exact same account can be added multiple times by clicking "Add an existing account" and authorizing it on the server. This is confusing as we have several accounts with similar icons.

Expected behavior

When authorized account, Elk checks if there is the same account in the account list and avoids adding to the new (duplicated) account. Instead, it should just switch to the existing profile.