Fix compatibility issues with Qt/PyQt6 versions

- Add null check for message.message in search filter
- Handle missing colorScheme/colorSchemeChanged methods for older Qt versions
- Add display check to prevent hanging in headless environments
- Update build documentation with system package alternative
- Update PyInstaller spec for Python 3.12
- Improve run.sh script with venv management

gotify_tray/gui/MainApplication.py

@@ -459,9 +459,10 @@ class MainApplication(QtWidgets.QApplication):
         self.main_window.hidden.connect(self.main_window_hidden_callback)
         self.main_window.activated.connect(self.tray.revert_icon)
 
-        self.styleHints().colorSchemeChanged.connect(
-            self.theme_change_requested_callback
-        )
+        if hasattr(self.styleHints(), "colorSchemeChanged"):
+            self.styleHints().colorSchemeChanged.connect(
+                self.theme_change_requested_callback
+            )
 
         self.messages_model.rowsInserted.connect(
             self.main_window.display_message_widgets