feat: show blocked_count in broadcast admin UI

- Add blocked_count to Broadcast interface
- 4-column stats grid with blocked card (warning color)
- Show blocked count in broadcast list when > 0
- Fetch single broadcast by ID instead of listing all
- Add i18n keys for blocked/blockedShort in ru/en/zh/fa

src/pages/AdminBroadcasts.tsx

@@ -217,6 +217,12 @@ export default function AdminBroadcasts() {
                     <span>{broadcast.target_type}</span>
                     <span>
                       {broadcast.sent_count}/{broadcast.total_count}
+                      {broadcast.blocked_count > 0 && (
+                        <span className="text-warning-400">
+                          {' '}
+                          ({broadcast.blocked_count} {t('admin.broadcasts.blockedShort')})
+                        </span>
+                      )}
                     </span>
                     <span>{new Date(broadcast.created_at).toLocaleDateString()}</span>
                   </div>