Fix profesional/especialidad: use MEDICO.CODIGO first, add config defaults

- SQL query now prioritizes MEDICO.CODIGO over RECEPCION.USUARIO as profesional
  (USUARIO is the billing clerk; MEDICO is the medical professional)
- Add profesional_default and especialidad_default config keys for when
  Firebird data is empty or contains invalid values (e.g. especialidad = ".")
- generar_rda_paciente accepts default_profesional and default_especialidad params
- ensure_defaults in queries.py now updates existing query records on startup

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

app/routes/config.py

@@ -23,6 +23,8 @@ DEFAULT_KEYS = [
     ("tns_password", "Nicolas2796*+"),
     ("num_documento_obligado", ""),
     ("cod_prestador", ""),
+    ("profesional_default", ""),
+    ("especialidad_default", ""),
 ]