- Rename AshAuthentication strategy from :oidc :rauthy to :oidc :oidc;
generated actions are now register_with_oidc / sign_in_with_oidc.
- Update config keys (:rauthy → :oidc) in dev.exs and runtime.exs.
- Update default_redirect_uri to /auth/user/oidc/callback everywhere.
- Rename Mv.Accounts helper functions accordingly.
- Update Mv.Secrets, AuthController, link_oidc_account_live and all tests.
- Update docker-compose.prod.yml, .env.example, README and docs.
IMPORTANT: OIDC providers must be updated to use the new redirect URI
/auth/user/oidc/callback instead of /auth/user/rauthy/callback.
OIDC_ADMIN_GROUP_NAME and OIDC_GROUPS_CLAIM were only set in prod block;
in dev admin_group was nil so role sync never ran. Move config outside
prod block so dev/test get ENV values.
