Centralize and standardize routing by introducing StaffPaths constants (shiftDetailsRoute, formI9, formW4) and using StaffPaths.childRoute in multiple staff feature modules instead of hardcoded paths. Add package:krow_core/core.dart imports where needed, clean up minor formatting/constructor spacing, make some route callbacks explicitly typed, replace shiftDetails string interpolation with the new constant, and remove a debug print from phone verification. These changes unify route definitions and add explicit tax-form routes (I-9 and W-4).