style(lists): apply gradient PageHeader to client/interest/yacht/company/berth lists

Pulls the polished gradient hero strip into the five primary list
surfaces. PR10b-e (detail polish, dashboard/admin polish, email +
notifications polish, mobile responsive sweep) deferred to a follow-up
release per spec risk register since visual baseline regen needs hands-
on iteration.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

src/components/clients/client-list.tsx

@@ -56,8 +56,7 @@ export function ClientList() {
   });
 
   const archiveMutation = useMutation({
-    mutationFn: (id: string) =>
-      apiFetch(`/api/v1/clients/${id}`, { method: 'DELETE' }),
+    mutationFn: (id: string) => apiFetch(`/api/v1/clients/${id}`, { method: 'DELETE' }),
     onSuccess: () => {
       queryClient.invalidateQueries({ queryKey: ['clients'] });
       setArchiveClient(null);
@@ -75,6 +74,7 @@ export function ClientList() {
       <PageHeader
         title="Clients"
         description="Manage your client records"
+        variant="gradient"
         actions={
           <PermissionGate resource="clients" action="create">
             <Button size="sm" onClick={() => setCreateOpen(true)}>
@@ -128,10 +128,7 @@ export function ClientList() {
         />
       )}
 
-      <ClientForm
-        open={createOpen}
-        onOpenChange={setCreateOpen}
-      />
+      <ClientForm open={createOpen} onOpenChange={setCreateOpen} />
 
       {editClient && (
         <ClientForm