Unify page layouts, compact headers and shared UI styling

frontend/app/ui/AdminShell.tsx

@@ -2,6 +2,7 @@
 
 import type { ReactNode } from 'react'
 import SettingsNavigation from './SettingsNavigation'
+import PageHeading from './PageHeading'
 
 type AdminShellProps = {
   title: string
@@ -16,14 +17,7 @@ export default function AdminShell({ title, subtitle, actions, rail, children }:
     <div className="admin-shell admin-shell--top-nav">
       <SettingsNavigation />
       <main className="card admin-card">
-        <div className="admin-header">
-          <div>
-            <span className="section-kicker">Configuration</span>
-            <h1>{title}</h1>
-            {subtitle && <p className="lede">{subtitle}</p>}
-          </div>
-          {actions}
-        </div>
+        <PageHeading title={title} description={subtitle} actions={actions} />
         {children}
         {rail && <details className="admin-supplemental"><summary>Additional information</summary>{rail}</details>}
       </main>