feat(sounds): add ru audio files for recording and live streaming notifications

[iospro]

Summary

• Added 4 Russian-language MP3 audio files for recording and live streaming
  notifications: recordingOn_ru.mp3, recordingOff_ru.mp3,
  liveStreamingOn_ru.mp3, liveStreamingOff_ru.mp3
• Added ru to the AudioSupportedLanguage enum in
  react/features/base/media/constants.ts so that getSoundFileSrc()
  correctly resolves _ru-suffixed file paths
• Language switching to/from Russian is fully handled by the existing
  shouldReloadAudioFiles() logic in base/sounds/middleware.any.ts
  via the AudioSupportedLanguage enum — no additional middleware changes required

[jitsi-jenkins]

Hi, thanks for your contribution!
If you haven't already done so, could you please make sure you sign our CLA (https://jitsi.org/icla for individuals and https://jitsi.org/ccla for corporations)? We would unfortunately be unable to merge your patch unless we have that piece :(.