feat(trakt): catalog API and shared catalog core (watchlist, discover, recommendations)

lib/services/trakt/trakt_page.dart

@@ -0,0 +1,23 @@
+import 'package:http/http.dart' as http;
+
+/// One page of a paginated Trakt response, parsed from the
+/// `X-Pagination-*` headers.
+class TraktPage<T> {
+  final List<T> items;
+  final int page;
+  final int pageCount;
+  final int itemCount;
+
+  const TraktPage({required this.items, required this.page, required this.pageCount, required this.itemCount});
+
+  bool get hasMore => page < pageCount;
+
+  /// Endpoints where pagination is optional omit the headers; default to a
+  /// single page so callers never loop.
+  factory TraktPage.fromResponse(http.Response res, List<T> items) => TraktPage(
+    items: items,
+    page: int.tryParse(res.headers['x-pagination-page'] ?? '') ?? 1,
+    pageCount: int.tryParse(res.headers['x-pagination-page-count'] ?? '') ?? 1,
+    itemCount: int.tryParse(res.headers['x-pagination-item-count'] ?? '') ?? items.length,
+  );
+}