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/main.dart

@@ -2,17 +2,24 @@
 
 import 'package:flutter/material.dart';
 import 'package:shared_preferences/shared_preferences.dart';
+import 'package:provider/provider.dart';
 
 import 'screens/home_screen.dart';
 import 'screens/home_desktop_screen.dart';
 import 'screens/login_screen.dart';
 import 'screens/desktop_login_screen.dart';
-import 'screens/responsive_layout.dart'; // keep this path if your file is under lib/screens/
+import 'screens/responsive_layout.dart';
 import 'core/theme_manager.dart';
+import 'core/analytics/posthog_service.dart';
+import 'features/auth/providers/auth_provider.dart';
+import 'features/gamification/providers/gamification_provider.dart';
+import 'features/booking/providers/checkout_provider.dart';
+import 'features/notifications/providers/notification_provider.dart';
 
 void main() async {
   WidgetsFlutterBinding.ensureInitialized();
   await ThemeManager.init(); // load saved theme preference
+  await PostHogService.instance.init();
 
   // Increase image cache for smoother scrolling and faster re-renders
   PaintingBinding.instance.imageCache.maximumSize = 500;
@@ -90,18 +97,26 @@ class MyApp extends StatelessWidget {
 
   @override
   Widget build(BuildContext context) {
-    return ValueListenableBuilder<ThemeMode>(
-      valueListenable: ThemeManager.themeMode,
-      builder: (context, mode, _) {
-        return MaterialApp(
-          title: 'Event App',
-          debugShowCheckedModeBanner: false,
-          theme: _lightTheme(),
-          darkTheme: _darkTheme(),
-          themeMode: mode,
-          home: const StartupScreen(),
-        );
-      },
+    return MultiProvider(
+      providers: [
+        ChangeNotifierProvider(create: (_) => AuthProvider()),
+        ChangeNotifierProvider(create: (_) => GamificationProvider()),
+        ChangeNotifierProvider(create: (_) => CheckoutProvider()),
+        ChangeNotifierProvider(create: (_) => NotificationProvider()),
+      ],
+      child: ValueListenableBuilder<ThemeMode>(
+        valueListenable: ThemeManager.themeMode,
+        builder: (context, mode, _) {
+          return MaterialApp(
+            title: 'Event App',
+            debugShowCheckedModeBanner: false,
+            theme: _lightTheme(),
+            darkTheme: _darkTheme(),
+            themeMode: mode,
+            home: const StartupScreen(),
+          );
+        },
+      ),
     );
   }
 }