refactor(ui): finish the page-header adoption and align the demote label

Route the notifications main view and the documents header through the
canonical page-header vocabulary the rest of the release adopted, and
align the admin demote-role label to the standard Nutzer term.

messages/de.json

@@ -5563,7 +5563,7 @@
     "userActions": "Aktionen",
     "editUser": "Nutzer bearbeiten",
     "editUserTitle": "Nutzer bearbeiten: {name}",
-    "demoteToUser": "Zu User degradieren",
+    "demoteToUser": "Zu Nutzer degradieren",
     "promoteToAdmin": "Zum Admin befördern",
     "toUser": "Zum Nutzer",
     "toAdmin": "Zum Admin",

src/app/notifications/page.tsx

@@ -187,14 +187,10 @@ export default function NotificationsPage() {
 
   return (
     <div className="space-y-6">
-      <div>
-        <h1 className="text-2xl font-bold tracking-tight">
-          {t("notifications.title")}
-        </h1>
-        <p className="text-muted-foreground text-sm">
-          {t("notifications.subtitle")}
-        </p>
-      </div>
+      <PageHeader
+        title={t("notifications.title")}
+        description={t("notifications.subtitle")}
+      />
 
       {/* Desktop: table layout */}
       <div className="bg-card border-border hidden overflow-hidden rounded-xl border md:block">

src/components/documents/inbound-documents-view.tsx

@@ -238,7 +238,9 @@ export function InboundDocumentsView() {
       <header className="flex items-center gap-3">
         <FileScan className="text-primary h-6 w-6" aria-hidden />
         <div>
-          <h1 className="text-xl font-semibold">{t("documents.title")}</h1>
+          <h1 className="text-2xl font-bold tracking-tight">
+            {t("documents.title")}
+          </h1>
           <p className="text-muted-foreground text-sm">
             {t("documents.subtitle")}
           </p>