Phase 2: API Layer Refactoring Complete - Refactored LastFM and Spotify clients to use BaseAPIClient, eliminated ~104 lines of duplicate code, unified HTTP handling and rate limiting

Phase 2.1: Core Agent Infrastructure Complete - PlannerAgent with strategic planning, Pydantic models, BaseAgent class, comprehensive tests (11/11 passing, 90% coverage)

feat: Complete Phase 1 - Foundation and API clients