Replace reconnect button emoji with sync icon

- Add static/icons/sync.png (24x24px)
- Use CSS filter to make icon green to match player theme

template/audio-player-frame.ctml

@@ -29,7 +29,7 @@
     <span class="now-playing-mini" id="mini-now-playing">Loading...</span>
     
     <button id="reconnect-btn" onclick="reconnectStream()" class="persistent-reconnect-btn" title="Reconnect if audio stops working">
-      🔄
+      <img src="/asteroid/static/icons/sync.png" alt="Reconnect" style="width: 18px; height: 18px; vertical-align: middle; filter: invert(48%) sepia(79%) saturate(2476%) hue-rotate(86deg) brightness(118%) contrast(119%);">
     </button>
     
     <button onclick="disableFramesetMode()" class="persistent-disable-btn">