Raise a Flutter macOS app's minimum deployment target to macOS 12 for Xcode 27
Xcode 27 refuses to build anything below macOS 12, and Flutter 3.47 moved its own floor from 10.15 to 12.0. What the automatic migration rewrites, the three places it silently skips (custom values, Podfile post_install overrides, plugin podspecs), and a Podfile fix for teams still on Flutter 3.44.