Use the new project description: Build Compose Multiplatform UIs in Python #82

The maintainer's decision (2026-10-03): the description is "Build Compose Multiplatform UIs in Python: Python Declarative UI Framework". The GitHub repository description is already changed. Done when pyproject's description, the README's first line, README_ko's matching sentence (합니다체, same meaning, not word for word) and the guide's front-page lead say it. PyPI shows it from the next version.