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/database/default_settings.py

@@ -5,7 +5,7 @@ from ..__version__ import __title__
 
 
 DEFAULT_SETTINGS = {
-    "theme": "default",
+    "theme": "automatic",
     "message/check_missed/notify": True,
     "logging/level": "Disabled",
     "export/path": os.path.join(