Have client fully serialise result

The results field in the `AnalysisResult` we get from the client is a string:
`'{"centre":-10.0,"peaks":[{"amplitude":1.0,"centre":-10.0,"fwhm":0.5,"normalised":true}],"scores":[1.0]}'`

This means we have to `json.loads` the result, it would be nice if the client fully serialised the result so it's already a dict.

## Acceptance Criteria
- The client returns results that don't need to be serialised

Start by locating the client code that constructs or returns AnalysisResult and inspect where the results field remains a JSON string. Check the existing client tests, if present, and verify that the returned results value is a dictionary without requiring json.loads; the acceptance criterion is that client results need no further serialization.

Written by the indexing model from the issue text.