ssh -T hg@bitbucket
You use hg@bitbucket when logging in via SSH, but in the remote URL you add to Git, you don’t specify a username. Since the configuration also does not include one, Git won’t know what username to log in with.
Change the URL to this:
git remote add origin git@bitbucket:ivanna/my-repo.git
Alternatively, you can add the user to the SSH config:
Host bitbucket
Hostname bitbucket.org
User git
IdentityFile /home/ivanna/.ssh/id_rsa_bitbucket
IdentitiesOnly yes