[Bug]: Pydantic serialization error

### What happened?

A bug happened with the BFF
/{version}/ecoindexes/latest

### Project

Ecoindex API

### What OS do you use?

_No response_

### urls

_No response_

### Relevant log output

```shell
ecoindex-api-backend | Expected `datetime` but got `str` - serialized value may not be as expected
ecoindex-api-backend | Expected `uuid` but got `str` - serialized value may not be as expected
ecoindex-api-backend | Expected `datetime` but got `str` - serialized value may not be as expected
ecoindex-api-backend | Expected `uuid` but got `str` - serialized value may not be as expected
ecoindex-api-backend | Expected `datetime` but got `str` - serialized value may not be as expected
ecoindex-api-backend | Expected `uuid` but got `str` - serialized value may not be as expected
ecoindex-api-backend | Expected `datetime` but got `str` - serialized value may not be as expected
ecoindex-api-backend | Expected `uuid` but got `str` - serialized value may not be as expected
ecoindex-api-backend | Expected `datetime` but got `str` - serialized value may not be as expected
ecoindex-api-backend | Expected `uuid` but got `str` - serialized value may not be as expected
ecoindex-api-backend | Expected `datetime` but got `str` - serialized value may not be as expected
ecoindex-api-backend | Expected `uuid` but got `str` - serialized value may not be as expected
ecoindex-api-backend | Expected `datetime` but got `str` - serialized value may not be as expected
ecoindex-api-backend | Expected `uuid` but got `str` - serialized value may not be as expected
ecoindex-api-backend | Expected `datetime` but got `str` - serialized value may not be as expected
ecoindex-api-backend | Expected `uuid` but got `str` - serialized value may not be as expected
ecoindex-api-backend | Expected `datetime` but got `str` - serialized value may not be as expected
ecoindex-api-backend | Expected `uuid` but got `str` - serialized value may not be as expected
ecoindex-api-backend | Expected `datetime` but got `str` - serialized value may not be as expected
ecoindex-api-backend | Expected `uuid` but got `str` - serialized value may not be as expected
ecoindex-api-backend | Expected `datetime` but got `str` - serialized value may not be as expected
ecoindex-api-backend | Expected `uuid` but got `str` - serialized value may not be as expected
ecoindex-api-backend | Expected `datetime` but got `str` - serialized value may not be as expected
ecoindex-api-backend | Expected `uuid` but got `str` - serialized value may not be as expected
ecoindex-api-backend | Expected `datetime` but got `str` - serialized value may not be as expected
ecoindex-api-backend | Expected `uuid` but got `str` - serialized value may not be as expected
ecoindex-api-backend | Expected `datetime` but got `str` - serialized value may not be as expected
ecoindex-api-backend | Expected `uuid` but got `str` - serialized value may not be as expected
ecoindex-api-backend | Expected `datetime` but got `str` - serialized value may not be as expected
ecoindex-api-backend | Expected `uuid` but got `str` - serialized value may not be as expected
ecoindex-api-backend | Expected `datetime` but got `str` - serialized value may not be as expected
ecoindex-api-backend | Expected `uuid` but got `str` - serialized value may not be as expected
ecoindex-api-backend | Expected `datetime` but got `str` - serialized value may not be as expected
ecoindex-api-backend | Expected `uuid` but got `str` - serialized value may not be as expected
ecoindex-api-backend | Expected `datetime` but got `str` - serialized value may not be as expected
ecoindex-api-backend | Expected `uuid` but got `str` - serialized value may not be as expected
ecoindex-api-backend | Expected `datetime` but got `str` - serialized value may not be as expected
ecoindex-api-backend | Expected `uuid` but got `str` - serialized value may not be as expected
ecoindex-api-backend | Expected `datetime` but got `str` - serialized value may not be as expected
ecoindex-api-backend | Expected `uuid` but got `str` - serialized value may not be as expected
ecoindex-api-backend | return self.serializer.to_python(
```

### Code of Conduct

- [X] I agree to follow this project's Code of Conduct

Reproduce the BFF /{version}/ecoindexes/latest request and inspect the route's Pydantic serialization path and response models. Trace why datetime and UUID values reach serialization as strings; done means the endpoint returns the expected response without the reported serialization warnings.

Written by the indexing model from the issue text.