Update US Default object for the calculate route request

[samau3]

Fixes #702

The status information for the calculate endpoints is determined by making a request to the endpoints with basic household data as an object with key value pairs. So if the endpoints have changed in regards to what keys and/or values it can accept, then this status page may incorrectly show an Error for the endpoint route. Therefore, the DEFAULT_US_HOUSEHOLD object needed to be updated to better match the expected data structure for the API.

🤖 Generated by Copilot at dece71d

Summary

Walkthrough

[MaxGhenis]

Will we need to update this each time we add/remove a variable from policyengine-us?

[anth-volk]

This is now engineered more flexibly so that the default household on the front end starts as an empty object, then variables are added with their default values to prevent breaking when variables are renamed in the country packages. Closing.