Create a company (société)
Creates a legal entity together with version 1 of its fiscal identity. id is caller-supplied — pick a stable, URL-safe slug; 409s when one already carries it. country is ISO-3166-1 alpha-2 and selects the profile that VALIDATES the identifiers: France is an instance, not the model. Identifiers are checked including their CHECK DIGITS — a SIREN that fails Luhn or a VAT number that is not the one built on that SIREN is a 400 with a field error, never a stored value. Every field except legalName and address.country is optional: an incomplete société is a legitimate state, reported through gaps, and is strictly better than an invented identifier.
Authorizations
Authorization: Bearer <token>. Accepts EITHER a Keycloak access token (scopes-in-token) OR an opaque POS session token; both resolve to the same pos.* scope vocabulary the route guards enforce.

