Add focused-window volume/mute control and app-group muting

- New active_window_volume/mute_active_window actions using kdotool to
  resolve the focused window under KWin/Wayland.
- New mute_group button action for muting multiple apps at once.
- New "binary:<name>" needle syntax to disambiguate generic Electron apps
  that share a PipeWire application.name with an unrelated app; fixes a bug
  where two knobs/groups matching the same generic name would fight over
  a stream's volume via the periodic reapply loop.
- Add kdotool to PKGBUILD depends, credit original author in README.

PKGBUILD

@@ -15,6 +15,7 @@ depends=(
     'uvicorn'
     'pipewire-pulse'
     'playerctl'
+    'kdotool'
 )
 makedepends=(
     'python-build'