feat: add complete review/rating system for events

New feature: Users can view, submit, and interact with event reviews.

Components added:
- ReviewModel, ReviewStatsModel, ReviewListResponse (models)
- ReviewService with getReviews, submitReview, markHelpful, flagReview
- StarRatingInput (interactive 5-star picker with labels)
- StarDisplay (read-only fractional star display)
- ReviewSummary (average rating + distribution bars)
- ReviewForm (star picker + comment field + submit/update)
- ReviewCard (avatar, timestamp, expandable comment, helpful/flag)
- ReviewSection (main container with pagination and state mgmt)

Integration:
- Added to LearnMoreScreen (both mobile and desktop layouts)
- Review API endpoints point to app.eventifyplus.com Node.js backend
- EventModel updated with averageRating/reviewCount fields

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

lib/features/reviews/services/review_service.dart

@@ -0,0 +1,104 @@
+// lib/features/reviews/services/review_service.dart
+import '../../../core/api/api_client.dart';
+import '../../../core/api/api_endpoints.dart';
+import '../models/review_models.dart';
+
+class ReviewService {
+  final ApiClient _api = ApiClient();
+
+  /// Fetch paginated reviews + stats for an event.
+  Future<ReviewListResponse> getReviews(int eventId, {int page = 1, int pageSize = 10}) async {
+    try {
+      final res = await _api.post(
+        ApiEndpoints.reviewList,
+        body: {'event_id': eventId, 'page': page, 'page_size': pageSize},
+        requiresAuth: true,
+      );
+
+      // Parse interactions map: { "review_id": { "helpful": bool, "flag": bool } }
+      final rawInteractions = res['interactions'] as Map<String, dynamic>? ?? {};
+      final interactionsMap = <int, Map<String, bool>>{};
+      rawInteractions.forEach((key, value) {
+        final id = int.tryParse(key);
+        if (id != null && value is Map) {
+          interactionsMap[id] = {
+            'helpful': value['helpful'] == true,
+            'flag': value['flag'] == true,
+          };
+        }
+      });
+
+      // Parse reviews
+      final rawReviews = res['reviews'] as List? ?? [];
+      final reviews = rawReviews.map((r) {
+        final review = Map<String, dynamic>.from(r as Map);
+        return ReviewModel.fromJson(review, interactions: interactionsMap[review['id']]);
+      }).toList();
+
+      // Parse stats
+      final stats = ReviewStatsModel.fromJson(res);
+
+      // Parse user's own review
+      ReviewModel? userReview;
+      if (res['user_review'] != null && res['user_review'] is Map) {
+        final ur = Map<String, dynamic>.from(res['user_review'] as Map);
+        userReview = ReviewModel.fromJson(ur, interactions: interactionsMap[ur['id']]);
+      }
+
+      return ReviewListResponse(
+        reviews: reviews,
+        stats: stats,
+        userReview: userReview,
+        total: (res['total'] as num?)?.toInt() ?? reviews.length,
+        page: (res['page'] as num?)?.toInt() ?? page,
+        pageSize: (res['page_size'] as num?)?.toInt() ?? pageSize,
+      );
+    } catch (e) {
+      throw Exception('Failed to load reviews: $e');
+    }
+  }
+
+  /// Submit or update a review.
+  Future<void> submitReview(int eventId, int rating, String? comment) async {
+    try {
+      await _api.post(
+        ApiEndpoints.reviewSubmit,
+        body: {
+          'event_id': eventId,
+          'rating': rating,
+          if (comment != null && comment.trim().isNotEmpty) 'comment': comment.trim(),
+        },
+        requiresAuth: true,
+      );
+    } catch (e) {
+      throw Exception('Failed to submit review: $e');
+    }
+  }
+
+  /// Toggle helpful vote on a review. Returns new helpful count.
+  Future<int> markHelpful(int reviewId) async {
+    try {
+      final res = await _api.post(
+        ApiEndpoints.reviewHelpful,
+        body: {'review_id': reviewId},
+        requiresAuth: true,
+      );
+      return (res['helpful_count'] as num?)?.toInt() ?? 0;
+    } catch (e) {
+      throw Exception('Failed to mark review as helpful: $e');
+    }
+  }
+
+  /// Flag a review for moderation.
+  Future<void> flagReview(int reviewId) async {
+    try {
+      await _api.post(
+        ApiEndpoints.reviewFlag,
+        body: {'review_id': reviewId},
+        requiresAuth: true,
+      );
+    } catch (e) {
+      throw Exception('Failed to flag review: $e');
+    }
+  }
+}