feat: get cards from backend

lib/feature/ranked/domain/entities/leaderboard.dart

@@ -0,0 +1,29 @@
+/// یک ردیف از جدولِ رتبه‌بندی.
+class RankEntry {
+  final int rank;
+  final String name;
+  final String avatar;
+  final int rankPoints;
+  final String tier; // bronze..king
+
+  RankEntry.fromJson(Map<String, dynamic> j)
+      : rank = (j['rank'] ?? 0) as int,
+        name = (j['name'] ?? '') as String,
+        avatar = (j['avatar'] ?? '') as String,
+        rankPoints = (j['rank_points'] ?? 0) as int,
+        tier = (j['tier'] ?? 'bronze') as String;
+}
+
+/// جدولِ رتبه‌بندیِ فصلِ جاری.
+class Leaderboard {
+  final int season;
+  final List<RankEntry> entries;
+  const Leaderboard(this.season, this.entries);
+
+  factory Leaderboard.fromJson(Map<String, dynamic> j) => Leaderboard(
+        (j['season'] ?? 1) as int,
+        ((j['entries'] as List?) ?? [])
+            .map((e) => RankEntry.fromJson(Map<String, dynamic>.from(e as Map)))
+            .toList(),
+      );
+}

lib/feature/ranked/domain/repository/ranked_repository.dart

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+import '../../../../core/resources/data_state.dart';
+import '../entities/leaderboard.dart';
+
+abstract class RankedRepository {
+  Future<DataState<Leaderboard>> getLeaderboard();
+}

lib/feature/ranked/domain/use_cases/get_leaderboard_usecase.dart

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+import '../../../../core/resources/data_state.dart';
+import '../../../../core/usecase/use_case.dart';
+import '../entities/leaderboard.dart';
+import '../repository/ranked_repository.dart';
+
+class GetLeaderboardUseCase
+    implements UseCase<DataState<Leaderboard>, NoParams> {
+  final RankedRepository repository;
+  GetLeaderboardUseCase(this.repository);
+
+  @override
+  Future<DataState<Leaderboard>> call(NoParams params) =>
+      repository.getLeaderboard();
+}