Restore dev purge protection

server.py

@@ -263,6 +263,9 @@ async def admin_delete_user(data: dict):
     if not target_user:
         return {"status": "fail", "message": "Target username required"}
 
+    if await asyncio.to_thread(core.is_developer, target_user):
+        return JSONResponse({"status": "error", "message": "Cannot purge a developer account"}, status_code=403)
+
     try:
         # 1. Evict via WebSocket first
         await coreHelper.evict_user_ws(target_user)