[Backend] Implement blockchain.service.ts — Stellar SDK Integration #82
Description
Description
blockchain.service.ts is 200+ lines of TODO comments with export default {}. This is the central blockchain integration layer — nothing works without it.
File: backend/src/services/blockchain.service.ts
Acceptance Criteria
- Initialize Stellar SDK with RPC endpoint, network passphrase, contract addresses
- Implement transaction builder with retry + exponential backoff
- Map contract errors to HTTP-friendly error messages
- Support both testnet and mainnet via env var
- Unit tests with mocked Stellar SDK
Priority
🔴 P0 — Critical — Entire backend blocked