Knowledge Gatherer API

Endpoints:
  POST /prompt - Send a prompt to query the news knowledge base
  POST /events/slack - Receive Slack webhook events
  GET  /gmail/auth - Get Gmail OAuth authorization URL
  GET  /gmail/redirect - Gmail OAuth callback handler
  GET  /health - Health check

Example:
  curl -X POST http://localhost:8080/prompt \
    -H "Content-Type: application/json" \
    -d '{"prompt": "What are the latest news about politics?"}'