Fix FCM Notifications Delivery App

I have a delivery-service app created with Manus AI and I’m struggling with Firebase Cloud Messaging: tokens are stored correctly in the database when users log in, yet no notification is actually shown on either Android or iOS. Because I’m not completely sure the in-app configuration is perfect, I need someone to trace the issue end-to-end—whether it lives in the Firebase console, the server logic that triggers the push, or the client-side handlers—and get reliable, real-time notifications working again.

What I expect from you:
• Inspect current Firebase setup, server keys, topics, APNs certificates and all platform-specific settings.
• Review and, if necessary, refactor the Manus AI generated code that registers the device, subscribes to topics and handles foreground/background messages.
• Provide a concise test plan and demonstrate notifications arriving on both Android and iOS builds (debug and production).
• Explain the fix in simple terms so I can maintain it going forward.

If you’ve solved similar cross-platform FCM problems before, I’d love to see a quick reference or short summary of what you did—no lengthy proposal needed, just proof you can get this done swiftly.