Hub: "give this user a Klonkt" from the users page
In hub mode each user on /admin/users gets a + button that opens the new-site
form with that user already pre-selected as owner (GET /admin/sites/new?owner=<id>,
validated via validOwnerId). Completes the owner-assignment flow: no longer only
accessible from the site form.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@…>