fix: blocking_lock panic in status(), fingerprint copy-to-clipboard

- Change status() from blocking_lock to async lock().await —
  fixes "Cannot block the current thread from within a runtime" panic
  that froze the call timer and broke audio
- Click fingerprint to copy to clipboard (both connect and settings screens)
- Show "Copied!" feedback on click

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

desktop/src-tauri/src/main.rs

@@ -108,7 +108,7 @@ async fn toggle_speaker(state: tauri::State<'_, Arc<AppState>>) -> Result<bool,
 async fn get_status(state: tauri::State<'_, Arc<AppState>>) -> Result<CallStatus, String> {
     let engine_lock = state.engine.lock().await;
     if let Some(ref engine) = *engine_lock {
-        let status = engine.status();
+        let status = engine.status().await;
         Ok(CallStatus {
             active: true,
             mic_muted: status.mic_muted,