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_rating_input.dart

@@ -0,0 +1,56 @@
+// lib/features/reviews/widgets/star_rating_input.dart
+import 'package:flutter/material.dart';
+
+class StarRatingInput extends StatelessWidget {
+  final int rating;
+  final ValueChanged<int> onRatingChanged;
+  final double starSize;
+
+  const StarRatingInput({
+    Key? key,
+    required this.rating,
+    required this.onRatingChanged,
+    this.starSize = 36,
+  }) : super(key: key);
+
+  static const _labels = ['', 'Poor', 'Fair', 'Good', 'Very Good', 'Excellent'];
+  static const _starGold = Color(0xFFFBBF24);
+  static const _starEmpty = Color(0xFFD1D5DB);
+
+  @override
+  Widget build(BuildContext context) {
+    return Column(
+      mainAxisSize: MainAxisSize.min,
+      children: [
+        Row(
+          mainAxisSize: MainAxisSize.min,
+          children: List.generate(5, (i) {
+            final starIndex = i + 1;
+            return GestureDetector(
+              onTap: () => onRatingChanged(starIndex),
+              child: Padding(
+                padding: const EdgeInsets.symmetric(horizontal: 2),
+                child: Icon(
+                  starIndex <= rating ? Icons.star_rounded : Icons.star_outline_rounded,
+                  size: starSize,
+                  color: starIndex <= rating ? _starGold : _starEmpty,
+                ),
+              ),
+            );
+          }),
+        ),
+        if (rating > 0) ...[
+          const SizedBox(height: 4),
+          Text(
+            _labels[rating],
+            style: TextStyle(
+              fontSize: 13,
+              fontWeight: FontWeight.w600,
+              color: _starGold,
+            ),
+          ),
+        ],
+      ],
+    );
+  }
+}