Refactor pagination logic in admin ads list keyboard

- Updated the pagination row to only display when multiple pages are available, improving the user interface for ad navigation.
- Enhanced the inline keyboard structure for better clarity and usability in the admin panel's ads management section.

bot/keyboards/inline/admin_keyboards.py

@@ -148,7 +148,8 @@ def get_ads_list_keyboard(
             callback_data=f"admin_ads:card:{c.ad_campaign_id}:{current_page}",
         )
 
-    # Pagination row
+    # Pagination row (only when needed)
+    if total_pages > 1:
         row = []
         if current_page > 0:
             row.append(