Revert "Add missing admin action files and navigation links"

This reverts commit 41be6835bf.

src/app/admin/import/effects/loading.tsx

@@ -1,14 +0,0 @@
-// src/app/[locale]/admin/import/effects/loading.tsx
-export default function Loading() {
-  return (
-    <div className="grid grid-cols-2 md:grid-cols-4 lg:grid-cols-6 gap-3">
-      {Array.from({ length: 18 }).map((_, i) => (
-        <div key={`effect-skeleton-${i}`} className="rounded-lg border bg-card p-3 animate-pulse">
-          <div className="h-12 w-12 bg-muted rounded mx-auto mb-2" />
-          <div className="h-4 bg-muted rounded w-3/4 mx-auto mb-1" />
-          <div className="h-7 bg-muted rounded" />
-        </div>
-      ))}
-    </div>
-  )
-}