feat(api): update DeviceLocation model and clean up AuthRepositoryImpl and BillingPageSkeleton

apps/mobile/packages/features/client/billing/lib/src/presentation/widgets/billing_page_skeleton/billing_page_skeleton.dart

@@ -19,7 +19,7 @@ class BillingPageSkeleton extends StatelessWidget {
         padding: const EdgeInsets.all(UiConstants.space5),
         child: Column(
           crossAxisAlignment: CrossAxisAlignment.start,
-          children: [
+          children: <Widget>[
             // Pending invoices section header
             const UiShimmerSectionHeader(),
             const SizedBox(height: UiConstants.space3),
@@ -39,7 +39,7 @@ class BillingPageSkeleton extends StatelessWidget {
               ),
               child: const Column(
                 crossAxisAlignment: CrossAxisAlignment.start,
-                children: [
+                children: <Widget>[
                   UiShimmerLine(width: 160, height: 16),
                   SizedBox(height: UiConstants.space4),
                   // Breakdown rows

apps/mobile/packages/features/client/billing/lib/src/presentation/widgets/billing_page_skeleton/breakdown_row_skeleton.dart

@@ -10,7 +10,7 @@ class BreakdownRowSkeleton extends StatelessWidget {
   Widget build(BuildContext context) {
     return const Row(
       mainAxisAlignment: MainAxisAlignment.spaceBetween,
-      children: [
+      children: <Widget>[
         UiShimmerLine(width: 100, height: 14),
         UiShimmerLine(width: 60, height: 14),
       ],