POST /api/blockchain/register — Register new user (RSA encrypted payload)POST /api/blockchain/transaction — Create transaction between walletsGET /api/blockchain/blocks — View all blocksGET /api/blockchain/report — Generate CSV donation reportcurl -X POST http://localhost:8080/api/blockchain/register \
-H "Content-Type: application/json" \
-d '{"username":"Alice","publicKey":""}'