feat(flutter): systemPlaylistsStatusProvider

Riverpod FutureProvider that reads the caller's system-playlists
build state. Consumed by the home Playlists row to decide between
real and placeholder cards.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

flutter_client/lib/playlists/playlists_provider.dart

@@ -1,8 +1,10 @@
 import 'package:flutter_riverpod/flutter_riverpod.dart';
 
+import '../api/endpoints/me.dart';
 import '../api/endpoints/playlists.dart';
 import '../library/library_providers.dart' show dioProvider;
 import '../models/playlist.dart';
+import '../models/system_playlists_status.dart';
 
 final playlistsApiProvider = FutureProvider<PlaylistsApi>((ref) async {
   return PlaylistsApi(await ref.watch(dioProvider.future));
@@ -17,3 +19,9 @@ final playlistDetailProvider =
     FutureProvider.family<PlaylistDetail, String>((ref, id) async {
   return (await ref.watch(playlistsApiProvider.future)).get(id);
 });
+
+final systemPlaylistsStatusProvider =
+    FutureProvider<SystemPlaylistsStatus>((ref) async {
+  final dio = await ref.watch(dioProvider.future);
+  return MeApi(dio).systemPlaylistsStatus();
+});