Automatic theme (#29)

* add "automatic" theme

set the theme and icons based on the system theme

* update the default icons based on system theme

* update pyqt to 6.5.0 to get the colorSchemeChanged callback

* rename style to theme

* remove unused svg files for default theme

* ServerInfoDialog: update feedback colors in dark mode

gotify_tray/gui/widgets/SettingsDialog.py

@@ -27,10 +27,12 @@ class SettingsDialog(QtWidgets.QDialog, Ui_Dialog):
     quit_requested = QtCore.pyqtSignal()
     theme_change_requested = QtCore.pyqtSignal(str)
 
-    def __init__(self):
+    def __init__(self, app: QtWidgets.QApplication):
         super(SettingsDialog, self).__init__()
         self.setupUi(self)
         self.setWindowTitle("Settings")
+        
+        self.app = app
 
         self.settings_changed = False
         self.changes_applied = False
@@ -104,6 +106,7 @@ class SettingsDialog(QtWidgets.QDialog, Ui_Dialog):
 
     def add_message_widget(self):
         self.message_widget = MessageWidget(
+            self.app,
             self,
             MessagesModelItem(
                 GotifyMessageModel(