refactor(admin): migrate section cards onto the shared card primitives

The admin tree hand-rolled its card surfaces and stepped padding at sm:
instead of md:, so it read denser than every other route on a tablet.
Move the sections onto SettingsCard/SettingsCardHeader and the mini-rows
onto ListRow; no behaviour, data, or copy changes.

src/components/admin/module-availability-section.tsx

@@ -4,6 +4,7 @@ import { useQuery, useMutation, useQueryClient } from "@tanstack/react-query";
 import { ToggleLeft } from "lucide-react";
 import { toast } from "sonner";
 
+import { SettingsCard } from "@/components/settings/settings-card";
 import { SettingsCardHeader } from "@/components/settings/_card-header";
 import { useTranslations } from "@/lib/i18n/context";
 import { queryKeys } from "@/lib/query-keys";
@@ -87,7 +88,7 @@ export function ModuleAvailabilitySection() {
   const availability = data?.availability;
 
   return (
-    <div className="bg-card border-border rounded-xl border p-4 sm:p-6">
+    <SettingsCard>
       <SettingsCardHeader
         icon={ToggleLeft}
         title={t("admin.modules.title")}
@@ -119,6 +120,6 @@ export function ModuleAvailabilitySection() {
             );
           })}
       </div>
-    </div>
+    </SettingsCard>
   );
 }