Mark Fitness setup as done

What your assistant is told

Mark the user's Loki Fitness setup as done, which takes the "finish setting up" card off their Home screen. Call it once, at the end of the first-run setup chat (the one the app opens with "I just set up Loki Fitness"), after you have gone through their profile and program with them and they have confirmed it looks right — or whenever they ask you to mark their setup as done. Don't call it just because a chat started. Takes no arguments. Idempotent: the first call records the time, later calls keep that first time and change nothing. Returns a one-line message you can repeat to the user and the time it was marked.