Create a new development script that provides the same functionality as yarn start but uses FEC's dev command instead of dev-proxy.

Acceptance Criteria:

1. Create a new command (suggested name: start:dev, dev, etc.) that:

• • Uses fec dev instead of fec dev-proxy
  • Maintains hot module reloading (HOT=true)

• • Runs the mock server concurrently (mockdata/mockserver.py)

• • Preserves the same concurrency setup (kill-others, prefix names, colors)

1. • Supports passthrough arguments
2. Document the difference between the new command and yarn start in the README or relevant documentation