Refactor widgets & imports; add krow_domain

Add local krow_domain dependency to client, staff apps and client home package. Numerous UI/widget cleanups across features: add const where applicable, use explicit List<Widget> types and List<Widget>.generate, add super.key to constructors, tighten BlocProvider generics, replace some Containers with SizedBox, and simplify InputDecoration/Border constructors. Fix API error handler to return a const UnknownException. Update internal imports to package-style paths (staff_home, staff_payments, staff_main repository interface) and normalize Flutter imports (use material.dart). Add missing braces for early returns in tax form pages. Mostly formatting and small API/typing refactors with no behavioral changes intended.

apps/mobile/packages/core/lib/src/services/api_service/mixins/api_error_handler.dart

@@ -97,7 +97,7 @@ mixin ApiErrorHandler {
         );
 
       case DioExceptionType.cancel:
-        return UnknownException(
+        return const UnknownException(
           technicalMessage: 'Request cancelled',
         );