feat(immersive): add multiple display modes like Cider

Display modes:
- Coverflow: centered album art with track info
- Split: artwork + panel side by side (current default)
- Lyrics Focus: single line at a time, large centered text
- Queue Focus: full screen queue view
- Visualizer Focus: full screen visualizer

Background:
- Heavy CSS blur (120px) for abstract color blobs
- No recognizable image, just colors

Keyboard shortcuts: 1-5 to switch modes

Inspired by Cider 3's immersive player design.

src/lib/components/immersive/panels/CoverflowPanel.svelte

@@ -0,0 +1,136 @@
+<script lang="ts">
+  import { BarChart2 } from 'lucide-svelte';
+
+  interface Props {
+    artwork: string;
+    trackTitle: string;
+    artist: string;
+    album?: string;
+    isPlaying?: boolean;
+  }
+
+  let {
+    artwork,
+    trackTitle,
+    artist,
+    album,
+    isPlaying = false
+  }: Props = $props();
+</script>
+
+<div class="coverflow-panel">
+  <div class="artwork-container" class:playing={isPlaying}>
+    <img src={artwork} alt={trackTitle} class="artwork" />
+  </div>
+
+  <div class="track-info">
+    {#if isPlaying}
+      <div class="now-playing-indicator">
+        <BarChart2 size={16} />
+      </div>
+    {/if}
+    <h1 class="track-title">{trackTitle}</h1>
+    <p class="track-artist">{artist}</p>
+    {#if album}
+      <p class="track-album">{album}</p>
+    {/if}
+  </div>
+</div>
+
+<style>
+  .coverflow-panel {
+    position: absolute;
+    inset: 0;
+    display: flex;
+    flex-direction: column;
+    align-items: center;
+    justify-content: center;
+    gap: 24px;
+    padding: 80px 40px 140px;
+    z-index: 5;
+  }
+
+  .artwork-container {
+    position: relative;
+    width: min(50vh, 400px);
+    height: min(50vh, 400px);
+    border-radius: 8px;
+    overflow: hidden;
+    box-shadow:
+      0 8px 32px rgba(0, 0, 0, 0.4),
+      0 16px 64px rgba(0, 0, 0, 0.2);
+    transition: transform 300ms ease;
+  }
+
+  .artwork-container:hover {
+    transform: scale(1.02);
+  }
+
+  .artwork {
+    width: 100%;
+    height: 100%;
+    object-fit: cover;
+  }
+
+  .track-info {
+    display: flex;
+    flex-direction: column;
+    align-items: center;
+    text-align: center;
+    gap: 6px;
+    max-width: 600px;
+  }
+
+  .now-playing-indicator {
+    display: flex;
+    align-items: center;
+    gap: 6px;
+    color: var(--accent-primary, #7c3aed);
+    margin-bottom: 4px;
+  }
+
+  .track-title {
+    font-size: clamp(20px, 3vw, 28px);
+    font-weight: 700;
+    color: var(--text-primary, white);
+    margin: 0;
+    text-shadow: 0 2px 10px rgba(0, 0, 0, 0.3);
+  }
+
+  .track-artist {
+    font-size: clamp(14px, 2vw, 18px);
+    color: var(--alpha-70, rgba(255, 255, 255, 0.7));
+    margin: 0;
+  }
+
+  .track-album {
+    font-size: clamp(12px, 1.5vw, 14px);
+    color: var(--alpha-50, rgba(255, 255, 255, 0.5));
+    margin: 0;
+    font-style: italic;
+  }
+
+  /* Responsive */
+  @media (max-width: 768px) {
+    .coverflow-panel {
+      padding: 70px 24px 130px;
+      gap: 20px;
+    }
+
+    .artwork-container {
+      width: min(60vw, 300px);
+      height: min(60vw, 300px);
+    }
+  }
+
+  @media (max-height: 600px) {
+    .artwork-container {
+      width: min(35vh, 250px);
+      height: min(35vh, 250px);
+    }
+
+    .track-info {
+      gap: 4px;
+    }
+  }
+</style>