azure-ad-sso-deferred-local-auth-v1-stub-interfaces

Azure AD SSO was deferred from R-Same v1 because Runwal’s Active Directory infrastructure work is incomplete. v1 ships local auth only: argon2id + TOTP MFA + JWT cookies. Stub interfaces for Azure AD OIDC/SAML2 are built into the auth module so the migration path (dual-mode → per-user email-match → deprecate local) can be wired without rework when AD is ready.