The EventCard logic assume interestedIds not being present means the
account can't set events as interested. Fix this logic by checking if
the account is valid instead and always have interestedIds present on
the account store.
An account refers to the user the active session is logged in as. As
such it doesn't make sense outside of the /auth API paths that deals
with the current authenticated user. Move /api/account to
/api/auth/account to reflect this.
