Model ID Not sync'd with externalized parameters for ECS Container

Reviewing the documentation: https://github.com/aws-samples/architecture-to-cloudformation/tree/main/agents-architecture-to-cloudformation

Based on Parameter #7, I expected that changing the Model ID would allow me to experiment with different models. Unfortunately that's not the case, instead the Streamlit container always tries to invoke: ```anthropic.claude-3-sonnet-20240229-v1:0```

It appears the Model ID is hardcoded [here](https://github.com/aws-samples/architecture-to-cloudformation/blob/6e1bb93471e82d7a8dd9e2a9125c8e5e706c97e5/agents-architecture-to-cloudformation/util/invoke/bedrock.py#L163C13-L163C20) in app.py

Requesting externalization of this parameter or sync with CFN.