feat: add descuento from RECEPCION.VALORDESC to RDA header

Pulls r.VALORDESC in all SQL queries (automation, test_rda, queries
defaults) and maps it to the top-level descuento field in the
RdaPaciente JSON encabezado.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

app/routes/queries.py

@@ -47,6 +47,7 @@ WHERE p.DOCIDENT = :doc_num""",
     r.CLASEPROC,
     r.HORAINICIORECEPCION,
     r.VALORTOTAL,
+    r.VALORDESC,
     rel.COD_EXAMEN,
     COALESCE(NULLIF(TRIM(ex.NUM_ISS), ''), TRIM(rel.COD_EXAMEN)) AS CUPS,
     rel.PRECIO,
@@ -80,6 +81,7 @@ WHERE r.NUM_FACTURA = :num_factura""",
     r.CLASEPROC,
     r.HORAINICIORECEPCION,
     r.VALORTOTAL,
+    r.VALORDESC,
     rel.COD_EXAMEN,
     COALESCE(NULLIF(TRIM(ex.NUM_ISS), ''), TRIM(rel.COD_EXAMEN)) AS CUPS,
     rel.PRECIO,