feat: Add full-screen receipt viewer, display trip participants in calendar, and restrict trip management options to creator.

lib/services/notification_service.dart

@@ -1,3 +1,4 @@
+import 'dart:convert';
 import 'dart:io';
 import 'package:cloud_firestore/cloud_firestore.dart';
 import 'package:firebase_messaging/firebase_messaging.dart';
@@ -49,7 +50,14 @@ class NotificationService {
       onDidReceiveNotificationResponse: (details) {
         // Handle notification tap
         LoggerService.info('Notification tapped: ${details.payload}');
-        // TODO: Handle local notification tap if needed, usually we rely on FCM callbacks
+        if (details.payload != null) {
+          try {
+            final data = json.decode(details.payload!) as Map<String, dynamic>;
+            _handleNotificationTap(data);
+          } catch (e) {
+            LoggerService.error('Error parsing notification payload', error: e);
+          }
+        }
       },
     );