I already have Firebase Cloud Messaging integrated in my Flutter application; what is missing is the custom audio experience. I’d like an experienced Flutter-Firebase developer to wire in MP3 sounds that play the moment a push message arrives. Here’s the behaviour I’m after: • Every incoming FCM should trigger a custom MP3 tone instead of the default system alert. • Different kinds of messages must be able to use different sounds, selected via keys in the payload (e.g. “chat”, “audio”, “video”). • The solution has to work on both Android notification channels and iOS notification categories, respecting platform-specific file format and naming conventions. You may assume the project builds and receives notifications already; your task is limited to adding the asset files, configuring Info.plist, AndroidManifest and channels, and demonstrating the correct sound plays on device. I’ll consider the job complete when I can send three test messages from Firebase Console, each tagged type A/B/C, and each one reliably triggers its own MP3 on my physical Android and iOS devices. Please let me know if you have shipped similar multi-sound FCM solutions in Flutter and how quickly you can turn this around.