Custom MFS Gateway and Android App

We are looking for an experienced Full-Stack Developer (or Agency) to build a custom, automated Mobile Financial Services (MFS) Payment Gateway system (similar to UddoktaPay / PayStation) supporting Bangladeshi payment methods: bKash, Nagad, Rocket, and Upay (both Personal and Agent numbers).
The system must include a customizable checkout page, three distinct web dashboards (Merchant, E-Wallet Agent, and Admin), REST APIs with Sandbox/Live modes, and a background Android SMS Listener App for automated payment verification.
Core System Components & Features:
1. Customizable Checkout & Payment Page
Clean, fast, and mobile-responsive payment UI (customizable branding/logo per merchant).
Displays dynamic MFS numbers (Personal/Agent) based on routing rules with copy-to-clipboard functionality.
Input fields for Customer Sender Number and Transaction ID (TrxID) with instant verification feedback.
2. Merchant / User Panel
Auth & KYC: Registration, Login, Forgot Password, and Email/Phone OTP verification.
Dashboard: Real-time analytics (Today's collection, total volume, success rate, available balance).
Developer Tools: API Key & Secret Key generation, Sandbox (Test) & Live mode toggle, Webhook URL configuration, and clear API integration documentation.
Transactions & Payouts: Detailed transaction logs with filters (TrxID, status, date) and withdrawal/payout request module.
3. E-Wallet Agent Panel (Number Providers)
Auth: Agent registration, login, and phone/NID verification.
Number Management: Agents can add their own bKash, Nagad, Rocket, or Upay (Personal/Agent) numbers, set daily transaction limits per number, and toggle active/inactive status.
Device Pairing: Option to pair their Android phone (via QR code or API token) with the SMS Reader App.
Earnings & Commission: Dedicated dashboard showing commission rates, how earnings work, per-transaction commission logs, and payout requests.
4. Super Admin Panel
Master Analytics: Total platform volume, net profit (commission spread), active merchants, and active agents.
Smart Number Routing: Algorithm to dynamically route checkout payments to active agent numbers based on daily limits, round-robin, or priority.
Management: Approve/reject merchants, agents, and submitted MFS numbers; manage global commission rates (Merchant fee vs. Agent commission); manual TrxID approval/dispute resolution; payout approvals.
5. Android SMS Listener / Reader App
Lightweight background Android app (Kotlin or Flutter) with foreground service to prevent OS battery killing.
Reads incoming official MFS SMS notifications (bKash, Nagad, Rocket, Upay), parses the Amount, Sender Number, and TrxID, and securely sends a POST request to our backend server via API to auto-approve matching pending transactions.
Preferred Tech Stack:
Backend: Laravel (PHP) or Node.js (NestJS/Express) with MySQL/PostgreSQL (Must handle database row-level locking/concurrency properly to prevent double-spending or duplicate TrxID approvals).
Frontend: Next.js / React or Vue.js with Tailwind CSS.
Mobile App: Native Android (Kotlin/Java) or Flutter.
Deliverables & Requirements:
1. Complete source code with clean documentation and deployment setup on our VPS (DigitalOcean/Hetzner).
2. Full database schema and Postman API collection.
3. Compiled APK + Source code for the Android SMS Reader App.

To Apply, Please Answer:
1. Have you previously built any automated MFS payment gateways, SMS-based verification systems, or fintech platforms? (Please share demos or screenshots).
2. Which tech stack do you recommend for this build and why?
3. What is your estimated timeline and milestone breakdown for completing all 4 modules?