Add interstitial endpoints and enhance media and template functionalities: implement MapInterstitialEndpoints in Program.cs, add preview functionality for media assets in MediaEndpoints, and introduce template preview capabilities in TemplateEndpoints. Remove obsolete bumper settings from Channel and related classes to streamline configuration.

frontend/src/routes/admin.tsx

@@ -29,6 +29,13 @@ function AdminLayout() {
         >
           {t('admin.shows.title')}
         </Link>
+        <Link
+          to="/admin/interstitials"
+          className={cn('pb-2 uppercase tracking-wide text-muted-foreground hover:text-foreground')}
+          activeProps={{ className: 'border-b-2 border-primary text-primary' }}
+        >
+          {t('admin.interstitials.title')}
+        </Link>
         <Link
           to="/admin/groups"
           className={cn('pb-2 uppercase tracking-wide text-muted-foreground hover:text-foreground')}

frontend/src/routes/admin/interstitials.tsx

@@ -0,0 +1,4 @@
+import { createFileRoute } from '@tanstack/react-router'
+import { InterstitialsPanel } from '@/features/admin/interstitials/InterstitialsPanel'
+
+export const Route = createFileRoute('/admin/interstitials')({ component: InterstitialsPanel })