Fix Qt WebEngine sandbox error when running as root

- Add QTWEBENGINE_DISABLE_SANDBOX=1 environment variable to all Qt WebEngine files
- Suppress Chromium sandbox warnings when running as root user
- Applied to: qt6_player.py, player.py, overlay_url_handler.py
- Environment variable set before any Qt imports to ensure effectiveness

mbetterclient/qt_player/overlay_url_handler.py

@@ -3,7 +3,14 @@ Custom URL scheme handler for serving overlay JavaScript files
 """
 
 import logging
+import os
 from pathlib import Path
+
+# Suppress Chromium sandbox warnings when running as root - MUST be set before Qt imports
+if os.geteuid() == 0:  # Running as root
+    os.environ['QTWEBENGINE_DISABLE_SANDBOX'] = '1'
+    print("Qt WebEngine sandbox disabled for root user")
+
 from PyQt6.QtCore import QBuffer, QIODevice, QByteArray
 from PyQt6.QtWebEngineCore import QWebEngineUrlRequestJob, QWebEngineUrlSchemeHandler
 

mbetterclient/qt_player/player.py

@@ -9,8 +9,15 @@ import logging
 import json
 import threading
 import signal
+import os
 from pathlib import Path
 from typing import Optional, Dict, Any, List
+
+# Suppress Chromium sandbox warnings when running as root - MUST be set before Qt imports
+if os.geteuid() == 0:  # Running as root
+    os.environ['QTWEBENGINE_DISABLE_SANDBOX'] = '1'
+    print("Qt WebEngine sandbox disabled for root user")
+
 from PyQt6.QtWidgets import (
     QApplication, QMainWindow, QWidget, QVBoxLayout, QHBoxLayout,
     QLabel, QPushButton, QSlider, QFrame, QStackedWidget

mbetterclient/qt_player/qt6_player.py

@@ -6,8 +6,15 @@ import sys
 import time
 import logging
 import json
+import os
 from pathlib import Path
 from typing import Optional, Dict, Any, List
+
+# Suppress Chromium sandbox warnings when running as root - MUST be set before Qt imports
+if os.geteuid() == 0:  # Running as root
+    os.environ['QTWEBENGINE_DISABLE_SANDBOX'] = '1'
+    print("Qt WebEngine sandbox disabled for root user")
+
 from PyQt6.QtWidgets import (
     QApplication, QMainWindow, QWidget, QVBoxLayout, QHBoxLayout,
     QLabel, QPushButton, QSlider, QFrame, QStackedWidget