feat: frontend productization with code review fixes
- Workflow: visual canvas, undo/redo, drag-and-drop, real-time execution WebSocket
- Evolution: dashboard, ECharts metrics, experience timeline, pitfall warnings, usage panel
- KB: source CRUD, document upload, search test
- Terminal: interactive PTY WebSocket, whitelist security
- Security: hmac.compare_digest, API key auth on all endpoints, whitelist bypass fix
- Fixes: ECharts async init, WebSocket intentional disconnect, TOCTOU race, Pydantic models
09698d7a06