feat: Add KILO_API_KEY to Docker configuration

Add Kilo Gateway API key support to Docker deployment:

- Add KILO_API_KEY environment variable to docker-compose.yml
- Add KILO_API_KEY to .env.example with documentation

This ensures the Kilo Gateway API key is properly passed through
to the Docker container when configured.

docker-compose.yml

@@ -118,6 +118,8 @@ services:
       - ROUTEWAY_API_KEY=${ROUTEWAY_API_KEY:-}
       # G4F
       - G4F_API_KEY=${G4F_API_KEY:-}
+      # Kilo Gateway
+      - KILO_API_KEY=${KILO_API_KEY:-}
       # Bytez
       - BYTEZ_API_KEY=${BYTEZ_API_KEY:-}
       # Ollama