Add Error and Loading States

Review Converter.js, Chart.js, and RatesTable.js.

For each API request, make sure the user can tell when data is loading, when fallback data is being used, and when historical data is temporarily unavailable.

Keep messages short and specific.

Test it

Use browser throttling or temporarily block an endpoint and observe each component’s fallback path.

Checkpoint

The application communicates external-data state instead of failing silently.