feat: Linux support, AMD ROCm, Whisper Turbo, and spawn fix

Cherry-picked and adapted from PR #89 and #214:

- Linux audio capture via PulseAudio/PipeWire monitor sources (cpal)
- AMD ROCm GPU support: HSA_OVERRIDE_GFX_VERSION env var, ROCm detection
- Whisper Turbo model (openai/whisper-large-v3-turbo) in all endpoints
- Cleaner Whisper language handling via generate_kwargs
- tauri::async_runtime::spawn fix to prevent panic on app shutdown
- Enable Linux (ubuntu-22.04) in release CI matrix

tauri/src-tauri/src/main.rs

@@ -792,7 +792,9 @@ pub fn run() {
                 });
 
                 // Wait for frontend response or timeout
-                tokio::spawn(async move {
+                // Use tauri::async_runtime::spawn instead of tokio::spawn to avoid
+                // panics when the Tokio runtime is being dropped during app shutdown
+                tauri::async_runtime::spawn(async move {
                     tokio::select! {
                         _ = rx.recv() => {
                             // Frontend responded, close window