health endpoint does not really provide insights about healthiness

### System Info

latest
any platform

### Information

- [ ] Docker + cli
- [ ] pip + cli
- [ ] pip + usage of Python interface

### Tasks

- [ ] An officially supported CLI command
- [ ] My own modifications

### Reproduction

1. check the code https://github.com/michaelfeil/infinity/blob/main/libs/infinity_emb/infinity_emb/infinity_server.py#L173
2. query `/health`

Start with infinity_emb/infinity_server.py around line 173 and query the /health endpoint to document its current behavior. The issue does not define which health signals or response details are required, so confirm the expected checks and response contract with maintainers; done should mean the endpoint provides the agreed health information.

Written by the indexing model from the issue text.