Document global invoice automation

[javorosas]

What

• Documents global invoice automation settings in the public organization API.
• Documents the 5,000-open-receipt batching behavior, repeated requests, and nullable completion response.
• Documents the existing public error code global_invoice_too_many_items with its receipt-based batching semantics.
• Documents group_similar_self_invoice_items and clarifies that it does not affect global invoices.
• Updates Spanish and English guides and OpenAPI definitions.

Why

This documents the public contract introduced by FacturAPI/facturapi#2123 without exposing internal automation implementation details.

Impact

The OpenAPI contract now exposes activate_global_invoice, group_similar_self_invoice_items, and limit_to_max_receipts. Existing receipt-settings examples now use the actual periodicity field. The guide points users to Dashboard receipt settings to monitor automatic and scheduled tasks.

Checks

• pnpm --dir website typecheck
• pnpm --dir website build
• OpenAPI YAML syntax validation
• git diff --check