feat(ui): add generated premium assets

lib/widgets/tarjeta_emisora.dart

@@ -293,25 +293,48 @@ class _TarjetaEmisoraState extends State<TarjetaEmisora> {
   }
 
   Widget _iconoFallback(double size) {
-    final t = context.pluriTokens;
-    return DecoratedBox(
-      decoration: BoxDecoration(
-        gradient: LinearGradient(
-          begin: Alignment.topLeft,
-          end: Alignment.bottomRight,
-          colors: [t.deepViolet, t.electricMagenta.withValues(alpha: 0.8)],
+    final art = _fallbackArtFor(widget.emisora.uuid);
+    return Stack(
+      fit: StackFit.expand,
+      children: [
+        Image.asset(
+          art,
+          fit: BoxFit.cover,
+          errorBuilder: (_, __, ___) => DecoratedBox(
+            decoration: BoxDecoration(
+              gradient: LinearGradient(
+                begin: Alignment.topLeft,
+                end: Alignment.bottomRight,
+                colors: [
+                  context.pluriTokens.deepViolet,
+                  context.pluriTokens.electricMagenta.withValues(alpha: 0.8),
+                ],
+              ),
+            ),
+          ),
         ),
-      ),
-      child: Center(
-        child: PluriIcon(
-          glyph: PluriIconGlyph.player,
-          variant: PluriIconVariant.filled,
-          size: size,
-          semanticLabel: 'Icono de emisora',
+        Center(
+          child: PluriIcon(
+            glyph: PluriIconGlyph.player,
+            variant: PluriIconVariant.activeGlow,
+            size: size,
+            semanticLabel: 'Icono de emisora',
+          ),
         ),
-      ),
+      ],
     );
   }
+
+  String _fallbackArtFor(String seed) {
+    const arts = [
+      'assets/images/station_art_aurora.png',
+      'assets/images/station_art_cosmic.png',
+      'assets/images/station_art_pulse.png',
+      'assets/images/station_art_nova.png',
+    ];
+    final index = seed.codeUnits.fold<int>(0, (a, b) => a + b) % arts.length;
+    return arts[index];
+  }
 }
 
 class _LiveBadge extends StatelessWidget {