feat: Phase 1 critical gaps — gamification API, Razorpay checkout, Google OAuth, notifications

- Fix gamification endpoints to use Node.js server (app.eventifyplus.com)
- Replace 6 mock gamification methods with real API calls (dashboard, leaderboard, shop, redeem, submit)
- Add booking models, service, payment service (Razorpay), checkout provider
- Add 3-step CheckoutScreen with Razorpay native modal integration
- Add Google OAuth login (Flutter + Django backend)
- Add full notifications system (Django model + 3 endpoints + Flutter UI)
- Register CheckoutProvider, NotificationProvider in main.dart MultiProvider
- Wire notification bell in HomeScreen app bar
- Add razorpay_flutter ^1.3.7 and google_sign_in ^6.2.2 packages

lib/features/gamification/models/gamification_models.dart

@@ -94,41 +94,162 @@ class UserGamificationProfile {
 }
 
 // ---------------------------------------------------------------------------
-// LeaderboardEntry
+// LeaderboardEntry — maps from Node.js API response fields
 // ---------------------------------------------------------------------------
 class LeaderboardEntry {
   final int rank;
   final String username;
   final String? avatarUrl;
   final int lifetimeEp;
+  final int monthlyPoints;
   final ContributorTier tier;
   final int eventsCount;
   final bool isCurrentUser;
+  final String? district;
 
   const LeaderboardEntry({
     required this.rank,
     required this.username,
     this.avatarUrl,
     required this.lifetimeEp,
+    this.monthlyPoints = 0,
     required this.tier,
     required this.eventsCount,
     this.isCurrentUser = false,
+    this.district,
   });
 
   factory LeaderboardEntry.fromJson(Map<String, dynamic> json) {
-    final ep = (json['lifetime_ep'] as int?) ?? 0;
+    // Node.js API returns 'points' for lifetime EP and 'name' for username
+    final ep = (json['points'] as num?)?.toInt() ?? (json['lifetime_ep'] as num?)?.toInt() ?? 0;
+    final tierStr = json['level'] as String? ?? json['tier'] as String?;
     return LeaderboardEntry(
-      rank: (json['rank'] as int?) ?? 0,
-      username: json['username'] as String? ?? '',
+      rank: (json['rank'] as num?)?.toInt() ?? 0,
+      username: json['name'] as String? ?? json['username'] as String? ?? '',
       avatarUrl: json['avatar_url'] as String?,
       lifetimeEp: ep,
-      tier: tierFromEp(ep),
-      eventsCount: (json['events_count'] as int?) ?? 0,
+      monthlyPoints: (json['monthlyPoints'] as num?)?.toInt() ?? 0,
+      tier: tierStr != null ? _tierFromString(tierStr) : tierFromEp(ep),
+      eventsCount: (json['eventsAdded'] as num?)?.toInt() ?? (json['events_count'] as num?)?.toInt() ?? 0,
       isCurrentUser: (json['is_current_user'] as bool?) ?? false,
+      district: json['district'] as String?,
     );
   }
 }
 
+/// Parse tier string from API (e.g. "Gold") to enum.
+ContributorTier _tierFromString(String s) {
+  switch (s.toLowerCase()) {
+    case 'diamond':  return ContributorTier.DIAMOND;
+    case 'platinum': return ContributorTier.PLATINUM;
+    case 'gold':     return ContributorTier.GOLD;
+    case 'silver':   return ContributorTier.SILVER;
+    default:         return ContributorTier.BRONZE;
+  }
+}
+
+// ---------------------------------------------------------------------------
+// CurrentUserStats — from leaderboard API's currentUser field
+// ---------------------------------------------------------------------------
+class CurrentUserStats {
+  final int rank;
+  final int points;
+  final int monthlyPoints;
+  final String level;
+  final int rewardCycleDays;
+  final int eventsAdded;
+  final String? district;
+
+  const CurrentUserStats({
+    required this.rank,
+    required this.points,
+    this.monthlyPoints = 0,
+    required this.level,
+    this.rewardCycleDays = 0,
+    this.eventsAdded = 0,
+    this.district,
+  });
+
+  factory CurrentUserStats.fromJson(Map<String, dynamic> json) {
+    return CurrentUserStats(
+      rank: (json['rank'] as num?)?.toInt() ?? 0,
+      points: (json['points'] as num?)?.toInt() ?? 0,
+      monthlyPoints: (json['monthlyPoints'] as num?)?.toInt() ?? 0,
+      level: json['level'] as String? ?? 'Bronze',
+      rewardCycleDays: (json['rewardCycleDays'] as num?)?.toInt() ?? 0,
+      eventsAdded: (json['eventsAdded'] as num?)?.toInt() ?? 0,
+      district: json['district'] as String?,
+    );
+  }
+}
+
+// ---------------------------------------------------------------------------
+// LeaderboardResponse — wraps the full leaderboard API response
+// ---------------------------------------------------------------------------
+class LeaderboardResponse {
+  final List<LeaderboardEntry> entries;
+  final CurrentUserStats? currentUser;
+  final int totalParticipants;
+
+  const LeaderboardResponse({
+    required this.entries,
+    this.currentUser,
+    this.totalParticipants = 0,
+  });
+}
+
+// ---------------------------------------------------------------------------
+// SubmissionModel — event submissions from dashboard API
+// ---------------------------------------------------------------------------
+class SubmissionModel {
+  final String id;
+  final String eventName;
+  final String category;
+  final String status; // PENDING, APPROVED, REJECTED
+  final String? district;
+  final int epAwarded;
+  final DateTime createdAt;
+  final List<String> images;
+
+  const SubmissionModel({
+    required this.id,
+    required this.eventName,
+    this.category = '',
+    required this.status,
+    this.district,
+    this.epAwarded = 0,
+    required this.createdAt,
+    this.images = const [],
+  });
+
+  factory SubmissionModel.fromJson(Map<String, dynamic> json) {
+    final rawImages = json['images'] as List? ?? [];
+    return SubmissionModel(
+      id: (json['id'] ?? json['submission_id'] ?? '').toString(),
+      eventName: json['event_name'] as String? ?? '',
+      category: json['category'] as String? ?? '',
+      status: json['status'] as String? ?? 'PENDING',
+      district: json['district'] as String?,
+      epAwarded: (json['total_ep_awarded'] as num?)?.toInt() ?? (json['ep_awarded'] as num?)?.toInt() ?? 0,
+      createdAt: DateTime.tryParse(json['created_at'] as String? ?? '') ?? DateTime.now(),
+      images: rawImages.map((e) => e.toString()).toList(),
+    );
+  }
+}
+
+// ---------------------------------------------------------------------------
+// DashboardResponse — wraps the full dashboard API response
+// ---------------------------------------------------------------------------
+class DashboardResponse {
+  final UserGamificationProfile profile;
+  final List<SubmissionModel> submissions;
+
+  const DashboardResponse({
+    required this.profile,
+    this.submissions = const [],
+  });
+}
+
 // ---------------------------------------------------------------------------
 // ShopItem — mirrors `RedeemShopItem` table
 // ---------------------------------------------------------------------------