feat(config): wire up wallpapers_dir, osd, window_switcher, global_menu settings

- wallpapers_dir: read from config, fallback ~/Pictures/Wallpapers
- osd: skip show_audio_osd/show_brightness_osd when disabled
- window_switcher: skip show_switcher when disabled
- global_menu_cache_enabled: bypass GTK class cache when false
- global_menu_method: control discovery strategies (auto/hyprland/dbus)

All keys added to constants.py defaults, settings UI, and config.toml

src/window/switcher/main.py

@@ -133,6 +133,8 @@ class ApplicationSwitcher(Window):
                 self._rebuild()
 
     def show_switcher(self) -> None:
+        if not config().get("window_switcher", True):
+            return
         self._rebuild()
         if not self.windows:
             return