Sign up a new company

Creates the account of a new company and emails it a link (and a code) to confirm the address and sign in; its organization is created on the first sign-in and waits for approval. Requires a Cloudflare Turnstile token solved for the signup action. An address that already has an invitation or an account gets its usual access link instead; the response is the same in every case. Personal email domains (gmail, hotmail, yahoo…) are refused where the deployment requires a company address. Rate limited per email (3 / 15 min) and per IP (10 / hour).