feat(mobile): swap admin page headers to PageHeader

Mechanical sweep replacing the plain h1+p header markup with the
mobile-aware PageHeader primitive across 12 admin pages: index,
backup, branding, documenso, email, import, invitations, monitoring,
onboarding, reminders, reports, webhooks. Webhooks "Add Webhook"
button preserved via the actions slot.

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

src/app/(dashboard)/[portSlug]/admin/reports/page.tsx

@@ -1,10 +1,12 @@
+import { PageHeader } from '@/components/shared/page-header';
+
 export default function ScheduledReportsPage() {
   return (
     <div className="space-y-6">
-      <div>
-        <h1 className="text-2xl font-bold text-foreground">Scheduled Reports</h1>
-        <p className="text-muted-foreground">Configure and manage automated report delivery</p>
-      </div>
+      <PageHeader
+        title="Scheduled Reports"
+        description="Configure and manage automated report delivery"
+      />
       <div className="flex flex-col items-center justify-center rounded-lg border border-dashed p-12">
         <p className="text-lg font-medium text-muted-foreground">Coming in Layer 3</p>
         <p className="text-sm text-muted-foreground">