[FIX] Add from_dict method to Entidad class for API compatibility

- Add from_dict classmethod to Entidad for proper data mapping
- Update get_entidades to use from_dict instead of direct kwargs
- Fix API response field mapping from 'codigoEntidad' to 'codigo_entidad'
- Maintain consistency with project's data model patterns
See also: #28

src/bcra_connector/bcra_connector.py

@@ -256,7 +256,7 @@ def get_entidades(self) -> List[Entidad]:
         self.logger.info("Fetching financial entities")
         try:
             data = self._make_request("cheques/v1.0/entidades")
-            entities = [Entidad(**e) for e in data["results"]]
+            entities = [Entidad.from_dict(e) for e in data["results"]]
             self.logger.info(f"Successfully fetched {len(entities)} entities")
             return entities
         except KeyError as e: