Sync Legacy Accounts

Operator-supplied input for a legacy account sync.

legacy_token is a bearer token for the legacy platform.gocrisp.com GraphQL gateway, pasted by the operator at sync time. That gateway is the old Firebase-backed API and does not accept the dock's Auth0 tokens, so the credential cannot be derived from the request's own Authorization header. When omitted, the backend falls back to the configured LEGACY_PLATFORM_BEARER_TOKEN.