Backend changes:
- Add device_bus and is_hardware fields to AudioDevice
- Parse PipeWire Flags (HARDWARE) and device.bus property from pactl output
Frontend changes:
- DeviceDropdown now supports both ALSA and PipeWire backends
- ALSA grouping: Defaults, Bit-perfect, Plugin Hardware, Other
- PipeWire grouping: Defaults, USB Audio (BP capable), HDMI/DisplayPort, Other HW, Virtual
- BP badge shown for USB Audio devices in PipeWire mode