Unify page layouts, compact headers and shared UI styling

frontend/app/admin/invites/page.tsx

@@ -1188,8 +1188,8 @@ export default function AdminInviteManagementPage() {
 
   return (
     <AdminShell
-      title="Invites"
-      subtitle="Create access links, apply account profiles, deliver invitations, and see what needs attention."
+      title="Invite policy & access"
+      subtitle="Manage account defaults, profiles, and invitations across Magent."
       rail={inviteManagementRail}
     >
       <section className="admin-section">

frontend/app/admin/requests-all/page.tsx

@@ -109,11 +109,6 @@ export default function AdminRequestsAllPage() {
     <AdminShell
       title="All requests"
       subtitle="Paginated view of every cached request."
-      actions={
-        <button type="button" onClick={() => router.push('/admin')}>
-          Back to settings
-        </button>
-      }
     >
       <section className="admin-section">
         <div className="admin-toolbar">

frontend/app/admin/system/page.tsx

@@ -116,14 +116,9 @@ export default function AdminSystemGuidePage() {
 
   return (
     <AdminShell
-      title="How it works"
-      subtitle="Admin-only service wiring, control areas, and recovery flow for Magent."
+      title="System guide"
+      subtitle="Service connections, controls, and recovery paths."
       rail={rail}
-      actions={
-        <button type="button" onClick={() => router.push('/admin')}>
-          Back to settings
-        </button>
-      }
     >
       <section className="admin-section system-guide">
         <div className="admin-panel">