Improve app_password lastLogin readability

The Dateformat of the last usage of the app password uses the format YYYYMM. This is confusing.

I propose to change it to YYYY-MM.

As far as i can see the change should be made in this line: <%= lastlogin %> --> "#{lastlogin[0..3]}-#{lastlogin[4..5]}"

As I do not know ruby I am hesitant to make a PR.

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