feat(ui): add stack icon to all 4 players

- Create StackIcon component with reactive context subscription
- Display Layers icon before track title when context exists
- Show tooltip with origin info on hover
- Add to: NowPlayingBar, ExpandedPlayer, FocusMode, MiniPlayer
- Icon hidden when no playback context (single track)
- Responsive sizing per player (14px-18px)

cp

src/lib/components/ExpandedPlayer.svelte

@@ -2,6 +2,7 @@
   import { invoke } from '@tauri-apps/api/core';
   import { X, Shuffle, SkipBack, Play, Pause, SkipForward, Repeat, Heart, List, Maximize2, MoreHorizontal, Cast } from 'lucide-svelte';
   import QualityBadge from './QualityBadge.svelte';
+  import StackIcon from './StackIcon.svelte';
   import LyricsLines from './lyrics/LyricsLines.svelte';
   import { startActiveLineUpdates } from '$lib/stores/lyricsStore';
 
@@ -244,7 +245,10 @@
         </div>
 
         <div class="track-info">
-          <h1 class="title">{trackTitle}</h1>
+          <div class="title-row">
+            <StackIcon size={18} class="stack-icon" />
+            <h1 class="title">{trackTitle}</h1>
+          </div>
           <h2 class="artist">{artist}</h2>
           <h3 class="album">{album}</h3>
           <div class="quality-info">
@@ -508,14 +512,27 @@
     width: 100%;
   }
 
+  .title-row {
+    display: flex;
+    align-items: center;
+    gap: 8px;
+    margin-bottom: 6px;
+  }
+
+  .title-row :global(.stack-icon) {
+    flex-shrink: 0;
+  }
+
   .title {
     font-size: 22px;
     font-weight: 600;
     color: white;
-    margin: 0 0 6px;
+    margin: 0;
     overflow: hidden;
     text-overflow: ellipsis;
     white-space: nowrap;
+    flex: 1;
+    min-width: 0;
   }
 
   .artist {

src/lib/components/FocusMode.svelte

@@ -1,5 +1,6 @@
 <script lang="ts">
   import { SkipBack, Play, Pause, SkipForward, ChevronDown } from 'lucide-svelte';
+  import StackIcon from './StackIcon.svelte';
   import LyricsLines from './lyrics/LyricsLines.svelte';
   import { startActiveLineUpdates, stopActiveLineUpdates } from '$lib/stores/lyricsStore';
   import { t } from '$lib/i18n';
@@ -184,7 +185,10 @@
       <div class="track-info">
         <img src={artwork} alt="" class="mini-artwork" />
         <div class="track-meta">
-          <div class="track-title">{trackTitle}</div>
+          <div class="track-title-row">
+            <StackIcon size={14} class="stack-icon" />
+            <div class="track-title">{trackTitle}</div>
+          </div>
           <div class="track-artist">{artist}</div>
         </div>
       </div>
@@ -464,6 +468,18 @@
     flex: 1;
   }
 
+  .track-title-row {
+    display: flex;
+    align-items: center;
+    gap: 6px;
+    white-space: nowrap;
+    overflow: hidden;
+  }
+
+  .track-title-row :global(.stack-icon) {
+    flex-shrink: 0;
+  }
+
   .track-title {
     font-size: 14px;
     font-weight: 600;
@@ -471,6 +487,8 @@
     white-space: nowrap;
     overflow: hidden;
     text-overflow: ellipsis;
+    flex: 1;
+    min-width: 0;
   }
 
   .track-artist {

src/lib/components/NowPlayingBar.svelte

@@ -20,6 +20,7 @@
   } from 'lucide-svelte';
   import QualityBadge from './QualityBadge.svelte';
   import AudioOutputBadges from './AudioOutputBadges.svelte';
+  import StackIcon from './StackIcon.svelte';
   import { t } from '$lib/i18n';
   import {
     subscribe as subscribeOffline,
@@ -294,7 +295,10 @@
           </button>
 
           <div class="song-info">
-            <span class="song-title" title={trackTitle}>{trackTitle}</span>
+            <div class="song-title-row">
+              <StackIcon size={14} class="stack-icon" />
+              <span class="song-title" title={trackTitle}>{trackTitle}</span>
+            </div>
             <div class="song-meta">
               {#if artist}
                 <button class="meta-link" onclick={onArtistClick} title={$t('actions.goToArtist')}>
@@ -676,6 +680,20 @@
     align-self: center;
   }
 
+  .song-title-row {
+    display: flex;
+    align-items: center;
+    gap: 6px;
+    white-space: nowrap;
+    overflow: hidden;
+    width: 100%;
+  }
+
+  .song-title-row :global(.stack-icon) {
+    flex-shrink: 0;
+    margin-top: 1px;
+  }
+
   .song-title {
     font-size: 13px;
     font-weight: 500;
@@ -683,6 +701,8 @@
     white-space: nowrap;
     overflow: hidden;
     text-overflow: ellipsis;
+    flex: 1;
+    min-width: 0;
   }
 
   .song-meta {

src/lib/components/StackIcon.svelte

@@ -0,0 +1,50 @@
+<script lang="ts">
+  import { Layers } from 'lucide-svelte';
+  import { subscribe, getCurrentContext, getContextDisplayInfo } from '$lib/stores/playbackContextStore';
+  import { onMount, onDestroy } from 'svelte';
+  
+  interface Props {
+    size?: number;
+    class?: string;
+  }
+  
+  let { size = 16, class: className = '' }: Props = $props();
+  
+  let context = $state(getCurrentContext());
+  let displayInfo = $state(context ? getContextDisplayInfo() : null);
+
+  let unsubscribe: (() => void) | null = null;
+
+  onMount(() => {
+    unsubscribe = subscribe(() => {
+      context = getCurrentContext();
+      displayInfo = context ? getContextDisplayInfo() : null;
+    });
+  });
+
+  onDestroy(() => {
+    unsubscribe?.();
+  });
+</script>
+
+{#if context && displayInfo}
+  <div class="stack-icon-wrapper {className}" title="Playing from: {displayInfo}">
+    <Layers size={size} strokeWidth={2} />
+  </div>
+{/if}
+
+<style>
+  .stack-icon-wrapper {
+    display: inline-flex;
+    align-items: center;
+    justify-content: center;
+    color: var(--text-secondary);
+    opacity: 0.7;
+    transition: opacity 0.2s;
+    flex-shrink: 0;
+  }
+  
+  .stack-icon-wrapper:hover {
+    opacity: 1;
+  }
+</style>

src/routes/miniplayer/+page.svelte

@@ -12,6 +12,7 @@
     Maximize2,
     ListMusic
   } from 'lucide-svelte';
+  import StackIcon from '$lib/components/StackIcon.svelte';
   import {
     subscribe as subscribePlayer,
     getPlayerState,
@@ -230,7 +231,10 @@
         <Maximize2 size={14} />
       </button>
       <div class="track-info">
-        <div class="title">{playerState.currentTrack?.title ?? 'No track'}</div>
+        <div class="title-row">
+          <StackIcon size={14} class="stack-icon" />
+          <div class="title">{playerState.currentTrack?.title ?? 'No track'}</div>
+        </div>
         <div class="artist-album">
           {playerState.currentTrack?.artist ?? '—'}
           {#if playerState.currentTrack?.album}
@@ -408,6 +412,18 @@
     padding-right: 30px;
   }
 
+  .title-row {
+    display: flex;
+    align-items: center;
+    gap: 6px;
+    white-space: nowrap;
+    overflow: hidden;
+  }
+
+  .title-row :global(.stack-icon) {
+    flex-shrink: 0;
+  }
+
   .title {
     font-weight: 600;
     font-size: 14px;
@@ -416,6 +432,8 @@
     text-overflow: ellipsis;
     color: #fff;
     line-height: 1.4;
+    flex: 1;
+    min-width: 0;
   }
 
   .artist-album {