Neither F-Droid nor Google Play renders Markdown in release notes, and both
cap them at 500 characters. Drop the Markdown header and bullets and trim the
copy to fit.
Bump versionCode to 13 and versionName to 3.0.0. The Flutter app ended at
2.0.0-alpha.3+12 (versionCode 12), so 13 keeps the eventual com.subtracks
release an in-place upgrade.
Metadata was still inherited from the Flutter app:
- add the changelog for versionCode 13
- rewrite the descriptions for the native app
- replace the Flutter phone screenshots with native renders, and mute the
screenshot fixture palette so the placeholder artwork reads as covers