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/features/client/hubs/lib/src/presentation/widgets/hubs_page_skeleton.dart

@@ -13,7 +13,7 @@ class HubsPageSkeleton extends StatelessWidget {
   Widget build(BuildContext context) {
     return UiShimmer(
       child: Column(
-        children: List.generate(5, (int index) {
+        children: List<Widget>.generate(5, (int index) {
           return Padding(
             padding: const EdgeInsets.only(bottom: UiConstants.space3),
             child: Container(
@@ -23,7 +23,7 @@ class HubsPageSkeleton extends StatelessWidget {
               ),
               padding: const EdgeInsets.all(UiConstants.space4),
               child: Row(
-                children: [
+                children: <Widget>[
                   // Leading icon placeholder
                   UiShimmerBox(
                     width: 52,
@@ -35,7 +35,7 @@ class HubsPageSkeleton extends StatelessWidget {
                   const Expanded(
                     child: Column(
                       crossAxisAlignment: CrossAxisAlignment.start,
-                      children: [
+                      children: <Widget>[
                         UiShimmerLine(width: 160, height: 16),
                         SizedBox(height: UiConstants.space2),
                         UiShimmerLine(width: 200, height: 12),