Replaces the native list with a combobox (name/code/CNPJ search, accent- and case-insensitive, keyboard + mouse, custom dropdown, hidden client_id = the Gerenciador's real CLIENTE.ID). The backend resolves client_id against the active GTI_GERENCIADOR mirror and rejects free text/unknown ids. Adds Tenant.external_cnpj (migration 0025) mirrored via the internal endpoint. Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>