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/index.html

@@ -79,13 +79,13 @@
             </div>
             <div class="vd-controls">
               <button id="vd-mic-btn" class="vd-btn" title="Mic (m)">
-                <span id="vd-mic-icon">&#x1F3A4;</span>
+                <span id="vd-mic-icon">Mic</span>
               </button>
               <button id="vd-spk-btn" class="vd-btn" title="Speaker (s)">
-                <span id="vd-spk-icon">&#x1F50A;</span>
+                <span id="vd-spk-icon">Spk</span>
               </button>
               <button id="vd-end-btn" class="vd-btn vd-end" title="Leave voice (q)">
-                <span>&#x26D4;</span>
+                <span>End</span>
               </button>
             </div>
           </div>