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/widgets/star_display.dart

@@ -0,0 +1,42 @@
+// lib/features/reviews/widgets/star_display.dart
+import 'package:flutter/material.dart';
+
+class StarDisplay extends StatelessWidget {
+  final double rating;
+  final double size;
+  final Color filledColor;
+  final Color emptyColor;
+
+  const StarDisplay({
+    Key? key,
+    required this.rating,
+    this.size = 16,
+    this.filledColor = const Color(0xFFFBBF24),
+    this.emptyColor = const Color(0xFFD1D5DB),
+  }) : super(key: key);
+
+  @override
+  Widget build(BuildContext context) {
+    return Row(
+      mainAxisSize: MainAxisSize.min,
+      children: List.generate(5, (i) {
+        final starPos = i + 1;
+        IconData icon;
+        Color color;
+
+        if (rating >= starPos) {
+          icon = Icons.star_rounded;
+          color = filledColor;
+        } else if (rating >= starPos - 0.5) {
+          icon = Icons.star_half_rounded;
+          color = filledColor;
+        } else {
+          icon = Icons.star_outline_rounded;
+          color = emptyColor;
+        }
+
+        return Icon(icon, size: size, color: color);
+      }),
+    );
+  }
+}