[Multi-User Part 5]: Add a production Docker file and use a gunicorn configuration with it (#514)

- Add a productionized setup for the Khoj server using `gunicorn` with multiple workers for handling requests
- Add a new Dockerfile meant for production config at `ghcr.io/khoj-ai/khoj:prod`; the existing Docker config should remain the same

.gitignore

@@ -21,7 +21,7 @@ todesktop.json
 khoj_assistant.egg-info
 /config/khoj*.yml
 .pytest_cache
-khoj.log
+*.log
 static
 
 # Obsidian plugin artifacts