Consent
What you agree to, and when. Each agreement is recorded with its version, so it is always clear what you accepted.
The Terms and the Privacy Policy, on Before you start, the first time you sign in.
Each agreement is saved with the document, its version, your language and the app you agreed in. Records are only ever added, never rewritten.
A new version asks you to agree again. Nothing changes behind your back.
The record of what you agreed to is kept for 10 years, the general limitation period under Swiss law, linked only to a one-way fingerprint of your email, then deleted.