refactor(navigation): reuse library icon mapping

lib/widgets/side_navigation_rail.dart

@@ -20,6 +20,7 @@ import '../providers/libraries_provider.dart';
 import '../services/music/music_playback_service.dart';
 import '../services/settings_service.dart';
 import '../utils/music_navigation.dart';
+import '../utils/content_utils.dart';
 import '../utils/platform_detector.dart';
 import '../utils/scroll_utils.dart';
 import '../utils/library_grouping.dart';
@@ -592,23 +593,6 @@ class SideNavigationRailState extends State<SideNavigationRail> with MountedSetS
     librariesProvider.refresh();
   }
 
-  IconData _getLibraryIcon(String type) {
-    switch (type.toLowerCase()) {
-      case 'movie':
-        return Symbols.movie_rounded;
-      case 'show':
-        return Symbols.tv_rounded;
-      case 'artist':
-        return Symbols.music_note_rounded;
-      case 'photo':
-        return Symbols.photo_rounded;
-      case 'mixed':
-        return Symbols.share_rounded;
-      default:
-        return Symbols.folder_rounded;
-    }
-  }
-
   /// Calculate top padding for macOS traffic lights
   double _getTopPadding(BuildContext context) {
     double basePadding = MediaQuery.paddingOf(context).top + 16;
@@ -1310,8 +1294,8 @@ class SideNavigationRailState extends State<SideNavigationRail> with MountedSetS
     return Padding(
       padding: const EdgeInsets.only(left: 12),
       child: NavigationRailItem(
-        icon: _getLibraryIcon(library.kind.id),
-        selectedIcon: _getLibraryIcon(library.kind.id),
+        icon: ContentTypeHelper.getLibraryIcon(library.kind.id),
+        selectedIcon: ContentTypeHelper.getLibraryIcon(library.kind.id),
         label: Column(
           crossAxisAlignment: .start,
           mainAxisSize: .min,

test/utils/content_utils_test.dart

@@ -1,4 +1,5 @@
 import 'package:flutter_test/flutter_test.dart';
+import 'package:material_symbols_icons/symbols.dart';
 import 'package:plezy/media/media_backend.dart';
 import 'package:plezy/media/media_item.dart';
 import 'package:plezy/media/media_item_types.dart';
@@ -96,5 +97,14 @@ void main() {
     test('isMusicLibrary returns false for null and non-matching types', () {
       expect(ContentTypeHelper.isMusicLibrary(null), isFalse);
     });
+
+    test('getLibraryIcon normalizes type and falls back to folder', () {
+      expect(ContentTypeHelper.getLibraryIcon('MOVIE'), Symbols.movie_rounded);
+      expect(ContentTypeHelper.getLibraryIcon('show'), Symbols.tv_rounded);
+      expect(ContentTypeHelper.getLibraryIcon('artist'), Symbols.music_note_rounded);
+      expect(ContentTypeHelper.getLibraryIcon('photo'), Symbols.photo_rounded);
+      expect(ContentTypeHelper.getLibraryIcon('mixed'), Symbols.share_rounded);
+      expect(ContentTypeHelper.getLibraryIcon('unknown'), Symbols.folder_rounded);
+    });
   });
 }