Flutter Developer – iOS & Android Subscription / In-App Purchase Integration

I have an existing Flutter/Firebase mobile application that is complete and being prepared for launch on the Apple App Store and Google Play Store. I need an experienced Flutter developer to implement the app's subscription/payment infrastructure on both platforms.

Required work:

Implement monthly and annual auto-renewing subscriptions for iOS and Android
Implement a configurable free trial
Integrate with Apple App Store and Google Play subscription systems
Add subscription/paywall and entitlement logic
Handle active, trial, canceled, expired, and failed-payment/grace-period states
Implement Restore Purchases
Ensure subscriptions are recognized appropriately across supported devices/accounts
Add a Manage Subscription option directing users to Apple/Google subscription management
Ensure pricing and free-trial settings can be changed through App Store Connect and Google Play Console without requiring an app update or developer changes for normal pricing adjustments
Do not hard-code subscription prices in the app; display applicable store pricing
Track trial starts, paid conversions, cancellations, and expirations in analytics
Test the complete purchase flow on both iOS and Android
Submit/update the production builds in both stores

Required experience: Flutter/Dart, Firebase, Apple StoreKit/App Store Connect, Google Play Billing/Play Console, mobile subscription entitlement management, and previous production subscription implementations.

Please provide examples of Flutter apps where you personally implemented subscriptions on both Apple and Google, explain the subscription architecture you used, and provide your fixed-price quote and estimated completion time.