This change revamps the internal logging architecture to be more flexible and descriptive. Previously all logs from both llama-swap and upstream services were mixed together. This makes it harder to troubleshoot and identify problems. This PR adds these new endpoints:
- `/logs/stream/proxy` - just llama-swap's logs
- `/logs/stream/upstream` - stdout output from the upstream server
* remove catch-all route to upstream proxy (it was broken anyways)
* add /upstream/:model_id to swap and route to upstream path
* add /upstream HTML endpoint and unlisted option
* add /upstream endpoint to show a list of available models
* add `unlisted` configuration option to omit a model from /v1/models and /upstream lists
* add favicon.ico
