feat(backend): add Node.js/TypeScript version with full parity

[miguelsilv]

🚀 Node.js/TypeScript Backend Implementation

This PR adds a full Node.js/TypeScript version of the existing Python backend, using the OpenAI Agents SDK for JavaScript.

✅ Implemented Features

Agents (5 total):

• Triage Agent - Main Routing
• Seat Booking Agent - Seat Reservation
• Flight Status Agent - Flight Status
• Cancellation Agent - Flight Cancellation
• FAQ Agent - Frequently Asked Questions

Tools (6 total):

• faq_lookup_tool - FAQ Search
• update_seat - Update Seat
• flight_status_tool - Flight Status
• baggage_tool - Baggage Information
• display_seat_map - Seat Map
• cancel_flight - Cancel Flight

Advanced Features:

• ✅ Persistent Conversation Memory
• ✅ Guardrails (Relevance + Anti-Jailbreak)
• ✅ Handoffs between Agents with Callbacks
• ✅ Dynamic Shared Context
• ✅ REST API identical to Python

🔧 Technical Changes

• Express.js + TypeScript
• Full typing with interfaces
• In-memory conversation store system
• Error handling and guardrails
• Full compatibility with existing UI

📖 Documentation

• Updated README with Node.js instructions
• One-liner command for quick start
• Documentation of all endpoints

🧪 How to Test

cd node-backend && OPENAI_API_KEY=your_key npm run dev

The API is available at http://localhost:8000 with the same interface as Python.

Tests:

• ✅ Multi-turn conversations with memory
• ✅ Handoffs between all agents
• ✅ Guardrails working
• ✅ Context persistence
• ✅ Tools running correctly