clinical_calc: Dart package for clinical formulas with explicit units and validated-range checks

clinical_calc is a pure Dart package providing clinical formulas, such as kidney function estimates, body size measures, unit conversions, dosing arithmetic and other scores. Its design targets common errors like mixing unit systems or applying adult equations to children, which can yield plausible but wrong results. Quantities carry explicit units, indexed and absolute GFR are distinct types, and invalid or out-of-range inputs raise typed exceptions. Every formula cites its original publication. The package is intended for qualified professionals, is not a medical device, provides no dosing recommendations, and requires results to be verified.