Flutter Developer for Mobile Template Customization

Hello! We are from Ukraine.
We're looking for an experienced Flutter developer to customize and adapt an existing mobile template for our "Private Reports" project. Our goal is to launch a cross-platform application (iOS/Android) for selling digital content. We've found something similar on CodeCanyon, specifically FluxStore Listing - The Best Directory WooCommerce app by Flutter, but we're unsure if this template will fully support the required functionality without significant modifications.
Please include in your proposal a specific template that you believe best fits our requirements, and that we can purchase.
Required App Functionality:
Backend (Firebase):
Firebase Authentication: For user management (registration, login, password recovery). Google Sign-In support is a plus.
Firestore: For storing metadata about reports (title, description, price, access status).
Firebase Storage: For hosting the actual report files (e.g., PDFs).
Monetization (CRITICAL!):
In-App Purchase (One-Time Purchase): The ability to sell each report individually via Google Play Billing (Android) and Apple App Store In-App Purchase (iOS). Subscriptions are not mandatory for the initial version, but their potential future support would be a benefit.
Content &User Management (Admin Panel):
A straightforward way to upload new reports, edit existing ones, manage prices, and perform basic user administration. We expect this to be handled either through the Firebase Console or via a simple web-based admin panel built on Firebase.
User Interface & Experience:
Simple User Profiles: For login, purchase history, and access to acquired reports only.
Report Access After Purchase: The ability to view the report file directly within the app or receive a link for download/viewing.
Interface Language: Exclusively English.
Features NOT Required (for simplification):
Complex user profiles.
Social features (comments, ratings).
Shopping cart system or multi-step checkout process.
Complex animations, gaming-specific functionality.
Integration with other payment gateways (Stripe, PayPal, etc.), apart from native In-App Purchase systems.
Your Proposal Must Include:
Template Name & Link: Specify a particular Flutter template (e.g., from CodeCanyon or another source) that you believe is the most suitable for our objectives.
Justification: Explain why this specific template is optimal based on our requirements (Firebase, In-App Purchase for digital content, admin panel).
Customization Assessment:
Which of our listed functionalities are already present "out-of-the-box" in this template?
Which functionalities would need to be customized/adapted? (e.g., In-App Purchase setup, admin panel adaptation for "reports").
What is the estimated complexity of these customizations, and what are your approximate timelines/costs for performing them (for your service)?
Ongoing Support: Do you provide consultation after the customization is complete, should we have questions about managing the project ourselves?
We're looking for an efficient solution with minimal modifications to launch our project quickly. We're open to discussions.
Thank you for your time and proposals!