Add audio server utilities module

Introduces a unified interface for working with PulseAudio and PipeWire
audio servers without requiring deep knowledge of either system.

Features:
- AudioServerUtils factory that auto-detects the running audio server
- PipewireUtils: Full support for PipeWire's device/profile/node hierarchy
- PulseaudioUtils: Support for PulseAudio sink/source management
- Node abstraction representing audio sinks and sources
- Methods to list, iterate, set default, and control volume of audio nodes
- CLI interface for listing and interactively selecting audio nodes

The iterator pattern (iter_sinks/iter_sources) automatically activates
profiles before yielding nodes, making them immediately usable.

Author: p-gentili