- 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/archive.php

@@ -14,7 +14,7 @@ if ($action === 'export') {
     $format = strtolower((string)($_GET['format'] ?? 'json'));
     $export = array_map(function(array $row) use ($canVoiceExport): array {
         $item = [
-            'id' => (int)$row['id'], 'group_id' => $row['group_id'] ? (int)$row['group_id'] : null,
+            'id' => (int)$row['id'],
             'username' => $row['username'], 'message' => $row['message'],
             'type' => $row['message_type'], 'created_at' => date(DATE_ATOM, (int)$row['created_at']),
         ];
@@ -28,9 +28,9 @@ if ($action === 'export') {
         header('Content-Type: text/csv; charset=utf-8');
         header('Content-Disposition: attachment; filename="' . $filename . '.csv"');
         $out = fopen('php://output', 'w');
-        fputcsv($out, ['id', 'group_id', 'username', 'message', 'type', 'created_at', 'voice_url']);
+        fputcsv($out, ['id', 'username', 'message', 'type', 'created_at', 'voice_url']);
         foreach ($export as $row) fputcsv($out, [
-            $row['id'], $row['group_id'], $row['username'], $row['message'], $row['type'],
+            $row['id'], $row['username'], $row['message'], $row['type'],
             $row['created_at'], $row['voice_url'] ?? '',
         ]);
         fclose($out);
@@ -44,7 +44,7 @@ if ($action === 'export') {
 
 $payload = array_map(function(array $row): array {
     return [
-        'id' => (int)$row['id'], 'group_id' => $row['group_id'] ? (int)$row['group_id'] : null,
+        'id' => (int)$row['id'],
         'message' => $row['message'], 'message_type' => $row['message_type'],
         'voice_url' => $row['message_type'] === 'voice' && !empty($row['voice_file']) ? voicePublicPath($row['voice_file']) : null,
         'voice_duration' => $row['voice_duration'] !== null ? (float)$row['voice_duration'] : null,