Closes #296

What has been done to verify that this works as intended?

• Use ONNX model to display model structure
• Update trainer to adapt the changes on data persistance.
• Add model structure API and remove mock data
• Use background tasks to execute training job after responding to the training request

Why is this the best possible solution? Were any other approaches considered?

How does this change affect users? Describe intentional changes to behavior and behavior that could have accidentally been affected by code changes. In other words, what are the regression risks?

Does this change require updates to documentation?

No

Before submitting this PR, please make sure you have:

• run python -m pytest tests/ and confirmed all checks still pass.
• verified that any code or assets from external sources are properly credited.