feat(ui): add now playing panel and context menu for tracks

src/lib/ToolBar.svelte

@@ -1,6 +1,8 @@
 <script lang="ts">
   import { beforeNavigate } from '$app/navigation';
 
+  let { onToggleNowPlaying }: { onToggleNowPlaying?: () => void } = $props();
+
   const icons = {
     back: '/icons/leftarrow.png',
     forward: '/icons/rightarrow.png',
@@ -36,6 +38,12 @@
     }
   }
 
+  function handleNowPlayingClick() {
+    if (onToggleNowPlaying) {
+      onToggleNowPlaying();
+    }
+  }
+
   $effect(() => {
     if (history.length === 0 && typeof window !== 'undefined') {
       history = [window.location.pathname];
@@ -64,7 +72,7 @@
 
   <div class="toolbar-separator"></div>
 
-  <button class="toolbar-button" disabled title="Now Playing">
+  <button class="toolbar-button" onclick={handleNowPlayingClick} title="Now Playing">
     <img src={icons.play} alt="Play" />
     <span>Now Playing</span>
   </button>