feat(reward): 新增客户端奖励中心

lib/core/data/remote/reward_api.dart

@@ -0,0 +1,30 @@
+// Author: fruit.com.cn
+
+import '../models/reward.dart';
+import 'api_client.dart';
+import 'response_decoders.dart';
+
+/// 奖励中心接口，对应契约 §1.8.1。
+class RewardApi {
+  const RewardApi(this._client);
+
+  final ApiClient _client;
+
+  Future<RewardOverview> overview(String locale) async {
+    final data = await _client.get(
+      '/app/rewards/overview',
+      query: {'locale': locale},
+    );
+    return RewardOverview.fromJson(ResponseDecoders.asMap(data));
+  }
+
+  Future<RewardActionResult> checkIn() async {
+    final data = await _client.post('/app/rewards/check-in');
+    return RewardActionResult.fromCheckin(ResponseDecoders.asMap(data));
+  }
+
+  Future<RewardActionResult> claim(String taskId) async {
+    final data = await _client.post('/app/rewards/tasks/$taskId/claim');
+    return RewardActionResult.fromClaim(ResponseDecoders.asMap(data));
+  }
+}