* feat!: replace legacy WebUI with unified FastAPI architecture #major
- Remove legacy WebUI (web/ package based on ThreadingHTTPServer)
- Unify CLI commands: --webui now seamlessly launches the new FastAPI service
- Migrate task service from web/services.py to src/services/task_service.py
- Update documentation to reflect the new simplified usage
* refactor(service): support parameterized query source in TaskService