Update .gitignore and remove obsolete cleanup documentation - Added `.gradio` and `tests/data/cache` to `.gitignore` to prevent unnecessary file tracking. Deleted outdated cleanup documentation files (`AGENT_CLEANUP_COMPLETION.md` and `CLEANUP_PLAN.md`) to streamline the codebase and remove obsolete references. This cleanup supports ongoing refactoring efforts and enhances overall project maintainability.
feat: Update environment configuration and documentation - Add Last.fm shared secret to env.example - Enhance README with Last.fm API key and shared secret details - Modify LastFmClient to accept shared secret as an optional parameter
