Evaluation: Clear error message

[AkhileshNegi]

Is your feature request related to a problem?
When you run an evaluation using a config with the GPT-4 Turbo model, the error message isn’t clear. It’s hard to tell what went wrong, which can confuse users and interrupt the workflow.

To Reproduce
Steps to reproduce the behavior:

1. Go to Config and create a new version using the GPT-4 Turbo model
2. Go to Evaluation → Text
3. Open the Evaluation tab
4. Add a name, pick a config, and select a dataset
5. Click “Run evaluation” — an error shows up in the right sidebar

Expected behavior
Running evaluation with Config should run successfully

Screenshots

[vprashrex]

The error happens because each provider only supports a specific set of models, using an unsupported model triggers a value error. The real issue is that we're returning raw str(e) in error responses across multiple places. we should sanitize these, log the full error internally and return only a clean, user-friendly message to the client.