fix(linux): resolve system audio device by stripping ' (System Audio)' display suffix

[90sRehem]

Fixes #701

Problem

On Linux, selecting any "System Audio" device in Settings and starting a recording never actually captures system audio, and no error is surfaced in the UI. The recording proceeds microphone-only.

Root cause

• configure_linux_audio() (frontend/src-tauri/src/audio/devices/platform/linux.rs) enumerates PulseAudio/PipeWire monitor sources and decorates their names with a " (System Audio)" suffix for display:

  format!("{} (System Audio)", name)

  This decorated string is what gets persisted to recording_preferences.json.

• At recording start, get_device_and_config() (frontend/src-tauri/src/audio/devices/configuration.rs) resolves the actual cpal device by exact string comparison against the raw cpal device name. The stored name still carries the " (System Audio)" suffix — only "(input)"/"(output)" suffixes are stripped in AudioDevice::from_name — so name == audio_device.name never matches and the function returns Err("Device not found: ...").

• That error is swallowed in AudioStreamManager::start_streams() (frontend/src-tauri/src/audio/stream.rs), which only logs a warning and continues with mic-only audio.

Net effect: no "System Audio" entry can ever be opened on Linux, regardless of which one is selected.

Fix

Strip the " (System Audio)" display suffix before comparing against the raw cpal device name, mirroring the existing "(input)"/"(output)" stripping already done in AudioDevice::from_name. This is an 11-line change confined to the Linux branch of get_device_and_config(); no other platforms are affected (the change is inside #[cfg(target_os = "linux")]).

Testing

• cargo check --lib passes on Linux with this change.
• Verified end-to-end on a PipeWire desktop: with the fix applied, starting a recording with a monitor source selected under "System Audio" now opens the capture stream successfully and the recorded file contains system audio; without the fix it fails silently as described in Linux: System Audio device is never resolved at recording start — system audio silently missing #701.