API: /auth/login: Provide a custom clientName for the API token list

[derf]

Issue: https://traewelling.de/settings lists all API Tokens as belonging to the "Träwelling Personal Access Client" service. When a user has logged into Traewelling via more than one API client, this makes it hard to revoke access to a specific app. It's also unclear which apps have been granted access to the user's Traewelling account.

Suggestion: Add clientName and (perhaps) URL parameters to /auth/login and list them in the API Token overview.