Add tests for audio server utilities

Comprehensive test coverage for the audio_server_utils module:

- NodeTests: Basic Node class instantiation
- AudioServerUtilsTests: Factory pattern and server detection
- PipewireUtilsTests: PipeWire-specific functionality including
  pw-dump parsing, device/profile/node handling, and volume control
- PulseaudioUtilsTests: PulseAudio-specific functionality including
  pactl parsing, sink/source management, and volume control

Author: p-gentili