Add CCTP REST API endpoints for initiating and tracking cross-chain USDC transfers

[grantfox-development]

Overview

Expose the CCTP service layer through versioned REST API endpoints so the frontend and external integrators can initiate, monitor, and complete cross-chain USDC transfers.

Endpoints to Implement

Method	Path	Description
POST	/api/v1/cctp/transfers	Initiate a new CCTP transfer
GET	/api/v1/cctp/transfers/:id	Get transfer status and details
GET	/api/v1/cctp/transfers	List transfers for the authenticated user/org
POST	/api/v1/cctp/transfers/:id/mint	Manually trigger mint step (for manual-relay flow)

Tasks

• Create CCTPController and register routes in the Express router
• Add request validation DTOs (amount, sourceChain, destinationStellarAddress)
• Add authentication middleware guard (organization role required)
• Return proper HTTP status codes and error payloads
• Add OpenAPI/Swagger annotations for all endpoints
• Rate-limit the POST /transfers endpoint to prevent abuse

Acceptance Criteria

• All endpoints return correct responses per the OpenAPI spec
• Invalid inputs return 400 with descriptive messages
• Unauthenticated requests return 401
• Swagger docs updated and accessible at /api/docs
• Controller layer has unit tests with mocked CCTPService