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.

.env.example

@@ -35,6 +35,9 @@ ROUTEWAY_API_KEY=
 # G4F (works without key for free tier)
 G4F_API_KEY=
 
+# Kilo Gateway - Universal AI Inference API (https://kilo.ai)
+KILO_API_KEY=
+
 # Bytez
 BYTEZ_API_KEY=