- Implemented.

Replaced polling with a single queued cursor worker, timeout recovery, 
backoff, deduplication, chronological insertion, and capped DOM history 
in cyberchat-v4.js.
Removed Groups UI, API, configuration, tier features, admin controls, 
and archive exposure.
Legacy group records remain stored but inaccessible.
Added configurable polling limits in config.json.

api/config.php

@@ -10,6 +10,8 @@ jsonResponse([
         'max_username_length' => $config['chat']['max_username_length'] ?? 12,
         'poll_interval_ms' => $config['chat']['poll_interval_ms'] ?? 2000,
         'poll_timeout_ms' => $config['chat']['poll_timeout_ms'] ?? 12000,
+        'poll_max_backoff_ms' => $config['chat']['poll_max_backoff_ms'] ?? 15000,
+        'max_rendered_messages' => $config['chat']['max_rendered_messages'] ?? 500,
     ],
     'ui' => $config['ui'] ?? [],
     'security' => ['min_password_length' => $config['security']['min_password_length'] ?? 4],
@@ -20,6 +22,5 @@ jsonResponse([
         'max_upload_bytes' => $config['voice']['max_upload_bytes'] ?? 12582912,
         'auto_play_default' => $config['voice']['auto_play_default'] ?? true,
     ],
-    'groups' => ['enabled' => $config['groups']['enabled'] ?? true],
     'subscriptions' => ['enabled' => $config['subscriptions']['enabled'] ?? true],
 ]);