- Change GET /api/me/deployments/:id/devices to return 400 error when legacy_deployment_id is missing
- Add error response with code 'MISSING_DEPLOYMENT_ID' and descriptive message
- Add comprehensive Jest tests for missing deployment scenarios
- Install Jest and Supertest for backend testing
- Add test scripts to package.json
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Co-Authored-By: Claude <noreply@anthropic.com>