- 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.

config.json

@@ -7,7 +7,9 @@
     "max_username_length": 12,
     "poll_interval_ms": 2000,
     "poll_timeout_ms": 12000,
+    "poll_max_backoff_ms": 15000,
     "messages_per_page": 100,
+    "max_rendered_messages": 500,
     "session_lock_ip": true,
     "session_lock_cookie": true,
     "allow_guest": false
@@ -24,9 +26,6 @@
     "auto_play_default": true,
     "upload_dir": "uploads/voice"
   },
-  "groups": {
-    "enabled": true
-  },
   "database": {
     "main_db": "db/chat.sqlite",
     "archive_path": "archive/{year}/{month}/{day}.sqlite",