Create companies in bulk

Creates up to 50 companies under the caller's agency in one request. Each item follows the exact same rules as POST /api/v1/companies (including the websiteUrl-or-linkedinUrl requirement, and the relationship default of none that keeps a company out of the default GET /api/v1/companies).

Items are processed independently and run a few at a time, so they do not necessarily complete in request order; results are always reported in request order via index. An item that fails — e.g. its websiteUrl / linkedinUrl already belongs to an existing company, it references an unknown custom attribute, or an unexpected internal error occurs — is reported in the response with status: "failed" and does not abort the remaining items. Internal errors carry a generic error message and are safe to retry only when the message says the item was not processed; when the failure happened after the company row was already persisted, the error says so and includes the created company id — do not retry that item as-is (its identity now exists, so a retry returns a conflict); verify the company and complete any missing fields via PATCH /api/v1/companies/{id} instead. Identity conflicts include the existing company id and should not be retried as-is.

The response is always 200 with one result per input item (matched by index, the zero-based position in the request array) plus a summary of created/failed counts. A request-level validation error (malformed item, more than 50 items, or the same company named by two items — see the request body) is rejected as a whole with 422 and creates nothing. Created items return the new company id only — read full details via GET /api/v1/companies/{id}.