- Remove `api_endpoint` from Settings model and settings UI
- Add `--llm-endpoint` / `AETHERA_LLM_ENDPOINT` and `--llm-key` /
`AETHERA_LLM_KEY` CLI flags (endpoint is required)
- Update client constructor to accept API key parameter
- Update tests and documentation to reflect new configuration approach
BREAKING CHANGE: LLM endpoint and key must now be provided via
`AETHERA_LLM_ENDPOINT` and `AETHERA_LLM_KEY` environment variables or
CLI flags instead of the Settings page.
