Rewrite in Rust, replacing Python implementation

- Replace Python (fonttools + sanic) with Rust (fontations + axum)
- Use read-fonts/write-fonts for font parsing and building
- Use ttf2woff2 for WOFF2 compression
- Remove OSS upload functionality
- Add comprehensive test suite (30 tests)
- Update README with bilingual (中文/English) documentation
- Rust edition 2024