feat(insights): first isights impemetation

test/fixtures/doubles/insights_doubles.dart

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+import 'dart:convert';
+import 'dart:io';
+
+import 'package:eatvio_app/features/insights/models/insights_payload_model.dart';
+import 'package:eatvio_app/features/insights/models/insights_period.dart';
+import 'package:eatvio_app/features/insights/repositories/insights_repository.dart';
+import 'package:flutter_test/flutter_test.dart';
+
+InsightsPayloadModel loadInsightsPayloadFixture([String name = 'insights_payload.json']) {
+  final json = jsonDecode(File('test/fixtures/insights/$name').readAsStringSync()) as Map<String, dynamic>;
+  return InsightsPayloadModel.fromJson(json);
+}
+
+/// Подмена [InsightsRepository] для виджет-тестов: без сети, с журналом вызовов.
+class FakeInsightsRepository extends Fake implements InsightsRepository {
+  FakeInsightsRepository({InsightsPayloadModel? payload, this.error, this.heightCm = 176}) : payload = payload ?? loadInsightsPayloadFixture();
+
+  InsightsPayloadModel payload;
+
+  /// Если задан — выбрасывается из [getInsights] (например, [InsightsForbidden]).
+  Object? error;
+  int? heightCm;
+
+  final List<({String? slug, BodyPeriod period})> insightsRequests = [];
+  final List<double> addedWeights = [];
+  final List<({int chest, int waist, int hip})> addedCircumferences = [];
+
+  @override
+  Future<int?> getHeightCm({String? slug}) async => heightCm;
+
+  @override
+  Future<InsightsPayloadModel> getInsights({String? slug, required BodyPeriod bodyPeriod, int? heightCm}) async {
+    insightsRequests.add((slug: slug, period: bodyPeriod));
+    final failure = error;
+    if (failure != null) {
+      throw failure;
+    }
+    return payload;
+  }
+
+  @override
+  Future<void> addWeight({required double weight}) async {
+    addedWeights.add(weight);
+  }
+
+  @override
+  Future<void> addCircumference({
+    required int chestCircumference,
+    required int waistCircumference,
+    required int hipCircumference,
+  }) async {
+    addedCircumferences.add((chest: chestCircumference, waist: waistCircumference, hip: hipCircumference));
+  }
+}