fix(ui): drawer buttons, stats fields, nicknames

- Buttons: use text labels (Mic/Spk/End) instead of emoji HTML
  entities that rendered as raw text on Android WebView
- Stats: match Rust CallStatus fields (tx_codec, rx_codec,
  encode_fps, recv_fps, audio_level, spk_muted)
- Nicknames: register_signal sends derive_alias() as the alias
  so other users see "Brave Falcon" instead of "a525:e9b2:..."
- Lobby header shows alias from get_app_info instead of raw fp
- pollStatus uses correct field names from Rust struct

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

desktop/src-tauri/src/lib.rs

@@ -1215,8 +1215,11 @@ fn do_register_signal(
     let transport = Arc::new(wzp_transport::QuinnTransport::new(conn));
     emit_call_debug(&app, "register_signal:quic_connected", serde_json::json!({ "relay": relay }));
 
+    // Send alias from seed-derived adjective+noun so other
+    // users see a friendly name in the lobby.
+    let alias = derive_alias(&seed);
     transport.send_signal(&SignalMessage::RegisterPresence {
-        identity_pub, signature: vec![], alias: None,
+        identity_pub, signature: vec![], alias: Some(alias),
     }).await.map_err(|e| format!("{e}"))?;
     emit_call_debug(&app, "register_signal:register_presence_sent", serde_json::json!({}));