[BACKEND] Add Support for Real-time FX Rate APIs (Multiple Providers)

[Wilfred007]

🛠 [BACKEND] Task Overview

This task focuses on the Node.js / Express / Prisma backend infrastructure for PayD.

📋 Requirements

• Maintain clean, modular code in the backend/ directory.
• Use Prisma for any database schema changes and migrations.
• Ensure all API endpoints follow standard security practices (auth, rate-limiting).
• Implement proper logging and error handling.

🛠 Technical Context

• Task: [BACKEND] Add Support for Real-time FX Rate APIs (Multiple Providers)
• Stack: Node.js, TypeScript, PostgreSQL, Prisma.
• Repository: Gildado/PayD

✅ Acceptance Criteria

• API endpoints are functional and tested.
• Proper error responses (4xx, 5xx) are implemented.
• Database migrations are provided if schema changed.
• Integration tests are included for new services.