Fix relay URL update using Qt signals for thread safety

QTimer.singleShot doesn't work properly from non-Qt threads.
Use Qt signals instead which are thread-safe and properly marshal
calls to the main thread.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

gui/main_window.py

@@ -121,6 +121,10 @@ class MainWindow(QMainWindow):
     """Main application window."""
 
     macros_changed = Signal()
+    # Signals for thread-safe relay status updates
+    relay_session_received = Signal(str)
+    relay_connected_signal = Signal()
+    relay_disconnected_signal = Signal()
 
     def __init__(self, app_dir: str):
         super().__init__()
@@ -160,6 +164,9 @@ class MainWindow(QMainWindow):
 
         # Connect signals
         self.macros_changed.connect(self.refresh_macros)
+        self.relay_session_received.connect(self._handle_relay_session)
+        self.relay_connected_signal.connect(lambda: self._update_relay_status(True))
+        self.relay_disconnected_signal.connect(lambda: self._update_relay_status(False))
 
         # Load initial data
         self.refresh_tabs()
@@ -659,18 +666,23 @@ class MainWindow(QMainWindow):
             self.status_bar.showMessage("Relay disconnected", 2000)
 
     def on_relay_connected(self):
-        """Handle relay connection established."""
-        QTimer.singleShot(0, lambda: self._update_relay_status(True))
+        """Handle relay connection established (called from background thread)."""
+        self.relay_connected_signal.emit()
 
     def on_relay_disconnected(self):
-        """Handle relay disconnection."""
-        QTimer.singleShot(0, lambda: self._update_relay_status(False))
+        """Handle relay disconnection (called from background thread)."""
+        self.relay_disconnected_signal.emit()
 
     def on_relay_session_id(self, session_id: str):
-        """Handle receiving session ID from relay."""
+        """Handle receiving session ID from relay (called from background thread)."""
         print(f"[DEBUG] on_relay_session_id called with: {session_id}")
+        self.relay_session_received.emit(session_id)
+
+    def _handle_relay_session(self, session_id: str):
+        """Handle relay session on main thread."""
+        print(f"[DEBUG] _handle_relay_session on main thread: {session_id}")
         self.settings_manager.set_relay_session_id(session_id)
-        QTimer.singleShot(0, self.update_ip_label)
+        self.update_ip_label()
 
     def _update_relay_status(self, connected: bool):
         """Update UI for relay status (called on main thread)."""