setup.md said Swarm SSO creates the operator's forge account, which was
not true until the previous commits. It now says how: sign in to the
forge once through authelia, then `swarmctl forge make-admin <you>`.
sso.md says what that first login does and why ACCOUNT_LINKING is
`login`. README, hivectl.md and forge.md drop `hivectl forge
create-user`, and the swarmctl README gains `forge make-admin`.
Refs #3782
0cbb7db2c0