fix: enforce semantic contrast across admin

src/app/admin/ads/page.tsx

@@ -61,10 +61,10 @@ export default async function AdminAds() {
                     {/* eslint-disable-next-line @next/next/no-img-element */}
                     <img src={ad.image} alt="" style={{ maxHeight: 40, maxWidth: 120 }} />
                   </td>
-                  <td className="text-sm text-gray-500 dark:text-gray-400 whitespace-nowrap">
+                  <td className="text-sm theme-text-muted dark:theme-text-muted whitespace-nowrap">
                     <code>{ad.image}</code>
                   </td>
-                  <td className="text-sm text-gray-500 dark:text-gray-400 whitespace-nowrap">
+                  <td className="text-sm theme-text-muted dark:theme-text-muted whitespace-nowrap">
                     {ad.createdAt ? ad.createdAt.toISOString().slice(0, 10) : "—"}
                   </td>
                   <td>