2) Crear Empresa

Ruta: POST /create-business (autenticado)
Rol: cualquiera sin empresa activa (luego queda como owner)

sequenceDiagram
  participant U as Usuario
  participant S as Flask
  participant DB as MySQL

  U->>S: POST /create-business (name, country, tax_doc_type, tax_id, ...)
  S->>S: Normaliza y valida Tax ID por país/tipo
  S->>DB: Verifica duplicados (country, tax_doc_type, tax_id)
  DB-->>S: OK
  S->>DB: INSERT login_business + linked_to_user(owner)
  DB-->>S: business_id
  S-->>U: {ok:true, business_id} → set session