Migrate Nativewind To Uniwind

This handles the full NativeWind to Uniwind migration, which is messier than it looks. It removes the old packages (including react-native-css-interop, which people constantly miss), converts your Tailwind 3 config to Tailwind 4's CSS-based theme system, replaces all cssInterop calls with withUniwind wrappers, and updates your Metro and Babel configs. The skill is thorough about the breaking changes, like ensuring your metro config uses relative paths for cssEntryFile and setting rem polyfills to 14 to match NativeWind's defaults. Most helpful if you're dealing with a codebase that has custom theme extensions or lots of third-party components wrapped with cssInterop, since that's where migrations usually break.