- terceros/transaccion: return clear error when required params (doc_num, num_factura) are missing instead of passing empty dict to Firebird causing Column unknown error
- transaccion: remove prefijo from 'por factura' query; parse num_factura as int when digit
- automation: add /preview endpoint to show patient/reception counts before sending; update UI with preview step and disabled run button until preview loads
- config: add TNS credentials section (tns_empresa, tns_usuario, tns_password, api_sucursal) with test-connection button
- config: add POST /config/test-tns endpoint
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
