fix: harden conveyor lab docs and build gate

[Mikecranesync]

Summary

• add the consolidated Hub and Conveyor Lab issue report without unrelated branch changes
• fix Conveyor Lab backend run-summary outcome typing so the backend TypeScript build passes
• align backend default port with documented/frontend proxy port 8888
• add Conveyor Lab docs for API, architecture, development, Modbus mapping, troubleshooting, security, support, roadmap, style, contributing, changelog, code of conduct, and license
• add a Conveyor Lab GitHub Actions workflow for backend and frontend builds

Verification

• cd apps/conveyor-lab/backend && npm run build
• cd apps/conveyor-lab/frontend && npm run build
• git diff --check --cached