docs(readme): rewrite to match current state (#10)

* docs(readme): rewrite to match current state

- reframe as download entry point + macOS update infrastructure
- fix scheduling: Cloudflare cron 15min primary + GitHub Actions 6h fallback
- document macOS Sparkle incremental auto-update + appcast endpoints
- document two-tier mirror with CF-IPCountry geo routing (R2 / S3)
- add capability table, star history chart, stars + MIT badges
- replace Community with Acknowledgements (LINUX DO + IHEP S3 mirror)
- drop sponsor placeholders

* docs(readme): add DuckCoding sponsor banner at top (bilingual, placeholder)

* docs(readme): switch DuckCoding sponsor to table layout with official logo

* docs(readme): simplify DuckCoding blurb to pay-as-you-go relay, drop region wording, larger EN text

* docs(readme): restore CN-specific wording for DuckCoding sponsor, keep EN generic

* docs(readme): add Star History section to English version for parity

* docs(readme): replace DuckCoding logo with user-provided ducklogo.jpg

* docs(readme): rewrite intro to neutral project description (CN+EN)

Author: Wangnov