Sign-up form as a LiveComponent.
Renders the email + password form when the password strategy is enabled, plus a stacked list of "Continue with X" buttons for every other configured strategy.
Strategy order is significant. EzAuth.Config.strategies/0 controls the
order of rendered sign-in option buttons, including the first buttons
shown before the user expands the full list.
When Password is not enabled, the form section is omitted and the
card becomes a launchpad of sign-in option buttons.
Profile fields (name, username) are not collected here; hosts collect
them post-login via EzAuth.Accounts.update_user_profile/2. Validation
delegates to EzAuth.Accounts.User.sign_up_changeset/1.
Usage
<.live_component module={EzAuth.UI.SignUp} id="sign-up" />