desktop: fix Windows per-app volume reset on video playback (#6852)

VideoPlayer's mediaPlayerReady listener called mediaPlayer.audio().setVolume(100)
on every freshly created VLC player. On Windows, VLCJ routes setVolume through
WASAPI's ISimpleAudioVolume, which is the per-app entry in the Windows Volume
Mixer — so every video playback snapped SimpleX Chat's mixer volume back to 100%,
overriding the user's own setting.

The call was also redundant: VLCJ's default volume for a new MediaPlayer is
already 100, and the only path that previously used setVolume (enableSound) has
been disabled since VLCJ issue #985 ("Impossible to change volume for only one
player. It changes for every player.").

Dropping the setVolume(100) line fixes the Windows regression without changing
playback loudness on any platform. AudioPlayer / SoundPlayer / CallSoundsPlayer
use a singleton VLC player and never called setVolume, so voice messages and
ringtones are unaffected.

Co-authored-by: Evgeny Poberezkin <evgeny@poberezkin.com>

apps/multiplatform/common/src/desktopMain/kotlin/chat/simplex/common/platform/VideoPlayer.desktop.kt

@@ -265,7 +265,9 @@ actual class VideoPlayer actual constructor(
         mediaPlayer().events().addMediaPlayerEventListener(object: MediaPlayerEventAdapter() {
           override fun mediaPlayerReady(mediaPlayer: MediaPlayer?) {
             playerThread.execute {
-              mediaPlayer?.audio()?.setVolume(100)
+              // Do not call setVolume here: on Windows VLCJ routes it through WASAPI ISimpleAudioVolume,
+              // which resets SimpleX Chat's per-app volume in the Windows Volume Mixer on every playback
+              // (VLCJ issue #985). A fresh VLCJ MediaPlayer already defaults to volume 100, so this was redundant.
               mediaPlayer?.audio()?.isMute = false
             }
           }