fix: use semantic colors across admin pages

src/app/admin/loading.tsx

@@ -3,7 +3,7 @@ export default function AdminLoading() {
     <div style={{ display: "flex", justifyContent: "center", padding: "4rem 0" }}>
       <div
         className="animate-spin w-8 h-8 border-4 rounded-full"
-        style={{ borderColor: "var(--color-primary)", borderTopColor: "transparent" }}
+        style={{ borderColor: "var(--admin-accent)", borderTopColor: "transparent" }}
       />
     </div>
   );