feat(pwa-offline): Pinia store + IndexedDB; contexto para cache/eliminación; toasts; compatibilidad PWA offline

- Agrega @pinia/nuxt, idb y store central (stores/music.ts)
- Cacheo manual desde menú contextual y borrado (TrackContextMenu)
- Ícono verde para canciones cacheadas, sin auto-cache al reproducir
- Toasts de feedback (stores/toast.ts, ToastContainer)
- Fallback offline de listado a IndexedDB; fix MUSIC_DIR absoluto en preview/prod
- Ajustes PWA: navigateFallback '/', devOptions, workbox condicional
- Estilos y animación del context menu (tema light/dark, blur fuerte)
- Correcciones de sintaxis y posicionamiento exacto al cursor

components/TrackListItem.client.vue

@@ -13,6 +13,7 @@
     @click="handleClick"
     @mouseenter="isHovered = true"
     @mouseleave="isHovered = false"
+    @contextmenu.prevent="handleContext"
   >
     <div class="track-info">
       <p class="track-name">{{ track.name }}</p>
@@ -25,7 +26,7 @@
         <AlertCircle v-if="hasError" class="icon error" :size="18" />
         <Pause v-else-if="isActive && !isPlaying" class="icon paused" :size="18" />
         <Play v-else-if="isActive && isPlaying" class="icon playing" :size="18" />
-        <Music v-else class="icon idle" :size="18" />
+        <Music v-else :class="['icon', 'idle', { cached: isCached }]" :size="18" />
       </div>
     </div>
 
@@ -60,10 +61,14 @@ const props = defineProps({
   hasError: {
     type: Boolean,
     default: false
+  },
+  isCached: {
+    type: Boolean,
+    default: false
   }
 })
 
-const emit = defineEmits(['click'])
+const emit = defineEmits(['click', 'context'])
 
 const isHovered = ref(false)
 
@@ -71,6 +76,10 @@ const handleClick = () => {
   emit('click', props.track)
 }
 
+const handleContext = (event) => {
+  emit('context', { track: props.track, x: event.clientX, y: event.clientY })
+}
+
 const formatTime = (seconds) => {
   if (!seconds || isNaN(seconds)) return '0:00'
   const mins = Math.floor(seconds / 60)
@@ -215,6 +224,10 @@ const formatTime = (seconds) => {
   opacity: 0.9;
 }
 
+.icon.idle.cached {
+  color: #22c55e; /* green-500 */
+}
+
 .loading-spinner {
   width: 20px;
   height: 20px;
@@ -284,4 +297,4 @@ const formatTime = (seconds) => {
     font-size: 1rem;
   }
 }
-</style>
+</style>