Add swingmusic-mobile submodule to replace Android app

- Updated .gitmodules to include mobile app submodule
- Added swingmusic_mobile directory with Flutter app
- Mobile app will now be built in unified release workflow

swingmusic_mobile/lib/data/models/search_suggestion_model.dart

@@ -0,0 +1,15 @@
+class SearchSuggestion {
+  final String id;
+  final String title;
+  final String? imageUrl;
+  final String type; // 'track', 'album', 'artist', 'playlist'
+  final dynamic data;
+
+  SearchSuggestion({
+    required this.id,
+    required this.title,
+    this.imageUrl,
+    required this.type,
+    this.data,
+  });
+}