Pireon OAuth clients allow a single grant type. With one PIREON_CLIENT_ID of
type password, email + password worked but "Sign in with Pireon" failed with
`unauthorized_client`.
- PIREON_CLIENT_ID/SECRET: authorization_code client (Sign in with Pireon,
Swagger UI). New PIREON_PASSWORD_CLIENT_ID/SECRET: password client, falling
back to the former so existing setups keep working.
- Refresh tries both clients: a refresh token only works with its issuer.
- PIREON_PASSWORD_GRANT=false now also rejects password grants in the API
(before it only hid the form).
- /api/auth/config returns clientId: null when there is no authorization_code
client, and the web hides "Sign in with Pireon".
- docker-compose passes the new variables; docs 05/07, .env.example,
openapi.json; unit tests for the client selection.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Josep Piguillem
cbaad17fc7