Release v0.2.0

Refactor AsyncTaskWorker into modular component system

This commit refactors the AsyncTaskWorker into a more modular, maintainable architecture.

Key changes include:

• Update README.md
• Split monolithic task_worker.py into specialized component modules
• Improve error handling with structured error categories and types
• Enhanced task cancellation with better queue state management
• Replace pickle serialization with more secure msgpack implementation
• Add improved progress tracking with throttling mechanism
• Update task_worker_api to use async pattern consistently
• Make task registry thread-safe with proper locking
• Update tests to match the new architecture
• Add comprehensive documentation for all components

The refactoring maintains API compatibility while improving internal structure, making the codebase easier to maintain and extend.