feat: dynamic library tabs and shared library navigation

- Replace hardcoded 4-tab system with data-driven visible tab list
- Shared libraries show only Browse + Playlists tabs
- Fix dpad navigation for shared libraries (no hidden tab targets)
- Switch to TickerProviderStateMixin to support tab controller recreation
- Navigate to library screen when tapping shared library sections
- Persist tab selection by name instead of index

lib/utils/content_utils.dart

@@ -60,6 +60,8 @@ class ContentTypeHelper {
         return Symbols.music_note_rounded;
       case 'photo':
         return Symbols.photo_rounded;
+      case 'mixed':
+        return Symbols.share_rounded;
       default:
         return Symbols.folder_rounded;
     }